/*++
  Copyright (c) 2016 Microsoft Corporation

  Module Name:

  theory_lra.cpp

  Abstract:

  <abstract>

  Author:

  Lev Nachmanson (levnach) 2016-25-3
  Nikolaj Bjorner (nbjorner)

  Revision History:


  --*/
#include "util/stopwatch.h"
#include "math/lp/indexed_value.h"
#include "math/lp/lar_solver.h"
#include "math/lp/nla_solver.h"
#include "math/lp/lp_types.h"
#include "math/lp/lp_api.h"
#include "math/polynomial/algebraic_numbers.h"
#include "math/polynomial/polynomial.h"
#include "util/nat_set.h"
#include "util/optional.h"
#include "util/inf_rational.h"
#include "util/cancel_eh.h"
#include "util/scoped_timer.h"
#include "util/nat_set.h"
#include "ast/ast_pp.h"
#include "model/numeral_factory.h"
#include "smt/smt_theory.h"
#include "smt/smt_context.h"
#include "smt/theory_lra.h"
#include "smt/smt_model_generator.h"
#include "smt/arith_eq_adapter.h"
#include "util/nat_set.h"
#include "ast/converters/generic_model_converter.h"
#include "ast/ast_pp.h"
#include "ast/ast_ll_pp.h"
#include "util/cancel_eh.h"
#include "util/scoped_timer.h"
#include "util/distribution.h"

typedef lp::lpvar lpvar;


namespace smt {

    typedef lp_api::bound<literal> api_bound;

    typedef ptr_vector<api_bound> lp_bounds;
    
class theory_lra::imp {        

    struct scope {
        unsigned m_bounds_lim;
        unsigned m_asserted_qhead;            
        unsigned m_asserted_atoms_lim;
    };

    struct delayed_atom {
        unsigned m_bv;
        bool     m_is_true;
        delayed_atom(unsigned b, bool t): m_bv(b), m_is_true(t) {}
    };

    class resource_limit : public lp::lp_resource_limit {
        imp& m_imp;
    public:
        resource_limit(imp& i): m_imp(i) { }
        bool get_cancel_flag() override { return !m_imp.m.inc(); }
    };

    theory_lra&                  th;
    ast_manager&                 m;
    arith_util                   a;
    arith_eq_adapter             m_arith_eq_adapter;
    vector<rational>             m_columns;
      

    // temporary values kept during internalization
    struct internalize_state {
        expr_ref_vector     m_terms;                     
        vector<rational>    m_coeffs;
        svector<theory_var> m_vars;
        ptr_vector<expr>    m_to_ensure_enode, m_to_ensure_var;
        internalize_state(ast_manager& m): m_terms(m) {}
        void reset() {
            m_terms.reset();
            m_coeffs.reset();
            m_vars.reset();
            m_to_ensure_enode.reset();
            m_to_ensure_var.reset();
        }
    };
    ptr_vector<internalize_state> m_internalize_states;
    unsigned                      m_internalize_head;

    class scoped_internalize_state {
        imp& m_imp;
        internalize_state& m_st;

        internalize_state& push_internalize(imp& i) {
            if (i.m_internalize_head == i.m_internalize_states.size()) {
                i.m_internalize_states.push_back(alloc(internalize_state, i.m));
            }
            internalize_state& st = *i.m_internalize_states[i.m_internalize_head++];
            st.reset();
            return st;
        }
    public:
        scoped_internalize_state(imp& i): m_imp(i), m_st(push_internalize(i)) {}
        ~scoped_internalize_state() { --m_imp.m_internalize_head; }
        expr_ref_vector&     terms() { return m_st.m_terms; }                     
        vector<rational>&    coeffs() { return m_st.m_coeffs; }
        svector<theory_var>& vars() { return m_st.m_vars; }
        ptr_vector<expr>&    to_ensure_enode() { return m_st.m_to_ensure_enode; }            
        ptr_vector<expr>&    to_ensure_var() { return m_st.m_to_ensure_var; }            
        void push(expr* e, rational c) { m_st.m_terms.push_back(e); m_st.m_coeffs.push_back(c); }
        void set_back(unsigned i) { 
            if (terms().size() == i + 1) return;
            terms()[i] = terms().back(); 
            coeffs()[i] = coeffs().back();
            terms().pop_back();
            coeffs().pop_back();
        }
    };
       
    typedef vector<std::pair<rational, lpvar>> var_coeffs;

    var_coeffs               m_left_side;              // constraint left side
    lpvar m_one_var;
    lpvar m_zero_var;
    lpvar m_rone_var;
    lpvar m_rzero_var;

    enum constraint_source {
        inequality_source,
        equality_source,
        definition_source,
        null_source
    };
    svector<constraint_source>                    m_constraint_sources;
    svector<literal>                              m_inequalities;    // asserted rows corresponding to inequality literals.
    svector<enode_pair>                           m_equalities;      // asserted rows corresponding to equalities.
    svector<theory_var>                           m_definitions;     // asserted rows corresponding to definitions

    svector<delayed_atom>  m_asserted_atoms;        
    ptr_vector<expr>       m_not_handled;
    ptr_vector<app>        m_underspecified;
    ptr_vector<app>        m_bv_terms;
    vector<ptr_vector<api_bound> > m_use_list;        // bounds where variables are used.

    // attributes for incremental version:
    u_map<api_bound*>      m_bool_var2bound;
    vector<lp_bounds>      m_bounds;
    unsigned_vector        m_unassigned_bounds;
    unsigned_vector        m_bounds_trail;
    unsigned               m_asserted_qhead;

    svector<unsigned>       m_bv_to_propagate;      // Boolean variables that can be propagated
    
    svector<std::pair<theory_var, theory_var> >       m_assume_eq_candidates; 
    unsigned                                          m_assume_eq_head;
    indexed_uint_set                                         m_tmp_var_set;
    
    unsigned                                          m_num_conflicts;

    // non-linear arithmetic
    scoped_ptr<nla::solver>  m_nla;

    // integer arithmetic
    scoped_ptr<lp::int_solver> m_lia;


    struct var_value_eq {
        imp & m_th;
        var_value_eq(imp & th):m_th(th) {}
        bool operator()(theory_var v1, theory_var v2) const { 
            if (m_th.is_int(v1) != m_th.is_int(v2)) {
                return false;
            }
            return m_th.is_eq(v1, v2);
        }
    };

    bool use_nra_model() const {
        return m_nla && m_nla->use_nra_model();
    }
    
    struct var_value_hash {
        imp & m_th;
        var_value_hash(imp & th):m_th(th) {}
        unsigned operator()(theory_var v) const { 
            if (m_th.use_nra_model()) 
                return m_th.is_int(v);
            else 
                return (unsigned)std::hash<lp::impq>()(m_th.get_ivalue(v)); 
        }
    };
    int_hashtable<var_value_hash, var_value_eq>   m_model_eqs;


    svector<scope>               m_scopes;
    lp_api::stats                m_stats;
    arith_factory*               m_factory;       
    scoped_ptr<lp::lar_solver>   m_solver;
    resource_limit               m_resource_limit;
    lp_bounds                    m_new_bounds;
    symbol                       m_farkas;
    vector<parameter>            m_bound_params;
    std_vector<lp::implied_bound>   m_implied_bounds;
    lp::lp_bound_propagator<imp> m_bp;

    context& ctx() const { return th.get_context(); }
    theory_id get_id() const { return th.get_id(); }
    theory_arith_params const& params() const { return ctx().get_fparams(); }
    bool is_int(theory_var v) const {  return is_int(get_enode(v));  }
    bool is_int(enode* n) const { return a.is_int(n->get_expr()); }
    bool is_real(theory_var v) const {  return is_real(get_enode(v));  }
    bool is_real(enode* n) const { return a.is_real(n->get_expr()); }
    enode* get_enode(theory_var v) const { return th.get_enode(v); }
    enode* get_enode(expr* e) const { return ctx().get_enode(e); }
    expr*  get_owner(theory_var v) const { return get_enode(v)->get_expr(); }
    enode_pp pp(enode* n) const { return enode_pp(n, ctx()); }
    enode_pp pp(theory_var v) const { return pp(get_enode(v)); }
    mk_bounded_pp bpp(expr* e) { return mk_bounded_pp(e, m); }

    lpvar add_const(int c, lpvar& var, bool is_int) {
        if (var != UINT_MAX) 
            return var;
        app_ref cnst(a.mk_numeral(rational(c), is_int), m);
        mk_enode(cnst);
        theory_var v = mk_var(cnst);
        var = lp().add_var(v, is_int);
        lp().push();
        add_def_constraint_and_equality(var, lp::GE, rational(c));
        add_def_constraint_and_equality(var, lp::LE, rational(c));
        TRACE("arith", tout << "add " << cnst << ", var = " << var << "\n";);
        return var;
    }

    lpvar get_one(bool is_int) {
        return add_const(1, is_int ? m_one_var : m_rone_var, is_int);
    }

    lpvar get_zero(bool is_int) {
        return add_const(0, is_int ? m_zero_var : m_rzero_var, is_int);
    }

    void ensure_nla() {
        if (!m_nla) {
            m_nla = alloc(nla::solver, *m_solver.get(), ctx().get_params(), m.limit());
            for (auto const& _s : m_scopes) {
                (void)_s;
                m_nla->push();
            }
            std::function<bool(lpvar)> is_relevant = [&](lpvar v) {
                theory_var u = lp().local_to_external(v);
                return ctx().is_relevant(th.get_enode(u));
            };
            m_nla->set_relevant(is_relevant);
        }
    }

    void found_unsupported(expr* n) {
        ctx().push_trail(push_back_vector<ptr_vector<expr>>(m_not_handled));
        TRACE("arith", tout << "unsupported " << mk_pp(n, m) << "\n");
        m_not_handled.push_back(n);
    } 

    void found_underspecified(expr* n) {
        if (a.is_underspecified(n)) {
            TRACE("arith", tout << "Unhandled: " << mk_pp(n, m) << "\n";);
            ctx().push_trail(push_back_vector<ptr_vector<app>>(m_underspecified));
            m_underspecified.push_back(to_app(n));
        }
        expr* e = nullptr, *x = nullptr, *y = nullptr;
        if (a.is_div(n, x, y)) {                
            e = a.mk_div0(x, y);
        }
        else if (a.is_idiv(n, x, y)) {                
            e = a.mk_idiv0(x, y);
        }
        else if (a.is_rem(n, x, y)) {
            n = a.mk_rem(x, a.mk_int(0));
            e = a.mk_rem0(x, a.mk_int(0));
        }
        else if (a.is_mod(n, x, y)) {                
            n = a.mk_mod(x, a.mk_int(0));
            e = a.mk_mod0(x, a.mk_int(0));
        }
        else if (a.is_power(n, x, y)) {                
            e = a.mk_power0(x, y);
        }
        if (e) {
            literal lit = th.mk_eq(e, n, false);
            ctx().mark_as_relevant(lit);
            ctx().assign(lit, nullptr);
        }

    }

    void linearize_term(expr* term, scoped_internalize_state& st) {
        st.push(term, rational::one());
        linearize(st);
    } 
        
    void linearize_ineq(expr* lhs, expr* rhs, scoped_internalize_state& st) {
        st.push(lhs, rational::one());
        st.push(rhs, rational::minus_one());
        linearize(st);
    }

    theory_var internalize_numeral(app* n, rational const& val) {

        if (!ctx().e_internalized(n))
            mk_enode(n);
        theory_var v = mk_var(n);
        lpvar vi = get_lpvar(v);
        if (vi == UINT_MAX) {
            vi = lp().add_var(v, a.is_int(n));
            add_def_constraint_and_equality(vi, lp::GE, val);
            add_def_constraint_and_equality(vi, lp::LE, val);
            register_fixed_var(v, val);
        }
        return v;
    }

        
    void linearize(scoped_internalize_state& st) { 
        expr_ref_vector & terms = st.terms();
        svector<theory_var>& vars = st.vars();
        vector<rational>& coeffs = st.coeffs();
        rational r;
        expr* n1, *n2;
        unsigned index = 0;
        while (index < terms.size()) {
            SASSERT(index >= vars.size());
            expr* n = terms.get(index);
            st.to_ensure_enode().push_back(n);
            if (a.is_add(n)) {
                for (expr* arg : *to_app(n)) {
                    st.push(arg, coeffs[index]);
                }
                st.set_back(index);
            }
            else if (a.is_sub(n)) {
                unsigned sz = to_app(n)->get_num_args();
                terms[index] = to_app(n)->get_arg(0);                    
                for (unsigned i = 1; i < sz; ++i) {
                    st.push(to_app(n)->get_arg(i), -coeffs[index]);
                }
            }
            else if (a.is_mul(n, n1, n2) && a.is_extended_numeral(n1, r)) {
                coeffs[index] *= r;
                terms[index] = n2;
                st.to_ensure_enode().push_back(n1);
            }
            else if (a.is_mul(n, n1, n2) && a.is_extended_numeral(n2, r)) {
                coeffs[index] *= r;
                terms[index] = n1;
                st.to_ensure_enode().push_back(n2);
            }
            else if (a.is_mul(n)) {
                theory_var v = internalize_mul(to_app(n));
                coeffs[vars.size()] = coeffs[index];
                vars.push_back(v);
                ++index;
            }
            else if (a.is_power(n, n1, n2) && is_app(n1) && a.is_extended_numeral(n2, r) && r.is_unsigned() && r.is_pos() && r <= 10) {
                theory_var v = internalize_power(to_app(n), to_app(n1), r.get_unsigned());
                coeffs[vars.size()] = coeffs[index];
                vars.push_back(v);
                ++index;
            }
            else if (a.is_numeral(n, r)) {
                theory_var v = internalize_numeral(to_app(n), r);
                coeffs[vars.size()] = coeffs[index];
                vars.push_back(v);
                ++index;
            }
            else if (a.is_uminus(n, n1)) {
                coeffs[index].neg();
                terms[index] = n1;
            }
            else if (a.is_to_real(n, n1)) {
                terms[index] = n1;
                if (!ctx().e_internalized(n)) {
                    app* t = to_app(n);
                    VERIFY(internalize_term(to_app(n1)));
                    mk_enode(t);
                    theory_var v = mk_var(n);
                    theory_var w = mk_var(n1);
                    lpvar vj = register_theory_var_in_lar_solver(v);
                    lpvar wj = register_theory_var_in_lar_solver(w);
                    auto lu_constraints = lp().add_equality(vj, wj);
                    add_def_constraint(lu_constraints.first);
                    add_def_constraint(lu_constraints.second);
                }
            }
            else if (is_app(n) && a.get_family_id() == to_app(n)->get_family_id()) {
                bool is_first = !ctx().e_internalized(n);
                app* t = to_app(n);
                internalize_args(t);
                mk_enode(t);
                theory_var v = mk_var(n);
                coeffs[vars.size()] = coeffs[index];
                vars.push_back(v);
                ++index;
                if (!is_first) {
                    // skip recursive internalization
                }
                else if (a.is_to_int(n, n1)) {
                    if (!ctx().relevancy())
                        mk_to_int_axiom(t);
                }
                else if (a.is_idiv(n, n1, n2)) {
                    if (!a.is_numeral(n2, r) || r.is_zero()) found_underspecified(n);
                    app_ref mod(a.mk_mod(n1, n2), m);
                    ctx().internalize(mod, false);
                    if (ctx().relevancy()) ctx().add_relevancy_dependency(n, mod);
                    if (m_nla && !a.is_numeral(n2)) {
                        // shortcut to create non-linear division axioms.
                        internalize_term(to_app(n));
                        internalize_term(to_app(n1));
                        internalize_term(to_app(n2));
                        theory_var q = mk_var(n);
                        theory_var x = mk_var(n1);
                        theory_var y = mk_var(n2);
                        m_nla->add_idivision(register_theory_var_in_lar_solver(q), register_theory_var_in_lar_solver(x), register_theory_var_in_lar_solver(y));
                    }
                    if (a.is_numeral(n2) && a.is_bounded(n1)) {
                        ensure_nla();
                        internalize_term(to_app(n));
                        internalize_term(to_app(n1));
                        internalize_term(to_app(n2));
                        theory_var q = mk_var(n);
                        theory_var x = mk_var(n1);
                        theory_var y = mk_var(n2);
                        m_nla->add_bounded_division(register_theory_var_in_lar_solver(q), register_theory_var_in_lar_solver(x), register_theory_var_in_lar_solver(y));
                    }
                }
                else if (a.is_mod(n, n1, n2)) {
                    if (!a.is_numeral(n2, r) || r.is_zero()) found_underspecified(n);
                    if (!ctx().relevancy()) mk_idiv_mod_axioms(n1, n2);    
                }
                else if (a.is_rem(n, n1, n2)) {
                    if (!a.is_numeral(n2, r) || r.is_zero()) found_underspecified(n);
                    if (!ctx().relevancy()) mk_rem_axiom(n1, n2);                    
                }
                else if (a.is_div(n, n1, n2)) {
                    if (!a.is_numeral(n2, r) || r.is_zero()) found_underspecified(n);
                    if (!ctx().relevancy()) mk_div_axiom(n1, n2);                    
                    st.to_ensure_var().push_back(n1);
                    st.to_ensure_var().push_back(n2);
                }
                else if (a.is_idiv0(n, n1, n2) || a.is_mod0(n, n1, n2)) {
                    st.to_ensure_var().push_back(n1);
                    st.to_ensure_var().push_back(n2);       
                }
                else if (a.is_power(n, n1, n2)) {                    
                    found_unsupported(n);
                    if (!ctx().relevancy()) mk_power_axiom(n, n1, n2);
                    st.to_ensure_var().push_back(n1);
                    st.to_ensure_var().push_back(n2);
                }
                else if (a.is_band(n) || a.is_shl(n) || a.is_ashr(n) || a.is_lshr(n)) {
                    m_bv_terms.push_back(to_app(n));
                    ctx().push_trail(push_back_vector(m_bv_terms));
                    mk_bv_axiom(to_app(n));
                    for (expr* arg : *to_app(n))
                        st.to_ensure_var().push_back(arg);                    
                }
                else if (!a.is_div0(n)) {
                    found_unsupported(n);
                }
                else {
                    // no-op
                }
            }
            else {
                if (is_app(n)) {
                    internalize_args(to_app(n));
                }
                if (m.is_ite(n)) {
                    if (!ctx().relevancy()) mk_ite_axiom(n);
                }
                theory_var v = mk_var(n);
                coeffs[vars.size()] = coeffs[index];
                vars.push_back(v);
                ++index;
            }
        }
        for (unsigned i = st.to_ensure_enode().size(); i-- > 0; ) {
            expr* n = st.to_ensure_enode()[i];
            if (is_app(n)) {
                mk_enode(to_app(n));
            }
        }
        st.to_ensure_enode().reset();
        for (unsigned i = st.to_ensure_var().size(); i-- > 0; ) {
            expr* n = st.to_ensure_var()[i];
            if (is_app(n)) {
                internalize_term(to_app(n));
            }
        }
        st.to_ensure_var().reset();
        
    }

    void internalize_args(app* t, bool force = false) {
        if (!force && !reflect(t)) 
            return;
        for (expr* arg : *t) {
            if (!ctx().e_internalized(arg)) {
                ctx().internalize(arg, false);
            }
        }
    }

    theory_var internalize_power(app* t, app* n, unsigned p) {
        internalize_args(t, true);
        bool _has_var = has_var(t);
        mk_enode(t);
        theory_var v = mk_var(t);
        if (_has_var)
            return v;
        VERIFY(internalize_term(n));
        theory_var w = mk_var(n);
        svector<lpvar> vars;
        for (unsigned i = 0; i < p; ++i) 
            vars.push_back(register_theory_var_in_lar_solver(w));
        ensure_nla();
        m_solver->register_existing_terms();
        m_nla->add_monic(register_theory_var_in_lar_solver(v), vars.size(), vars.data());
        return v;
    }

    theory_var internalize_mul(app* t) {
        SASSERT(a.is_mul(t));
        internalize_args(t, true);
        bool _has_var = has_var(t);
        mk_enode(t);
        theory_var v = mk_var(t);

        if (!_has_var) {
            svector<lpvar> vars;
            for (expr* n : *t) {
                if (is_app(n)) VERIFY(internalize_term(to_app(n)));
                SASSERT(ctx().e_internalized(n));
                theory_var v = mk_var(n);
                vars.push_back(register_theory_var_in_lar_solver(v));
            }
            TRACE("arith", tout << "v" << v << " := " << bpp(t) << "\n" << vars << "\n";);
            m_solver->register_existing_terms();
            ensure_nla();
            m_nla->add_monic(register_theory_var_in_lar_solver(v), vars.size(), vars.data());
        }
        return v;
    }

    enode * mk_enode(app * n) {
        TRACE("arith_verbose", tout << bpp(n) << " internalized: " << ctx().e_internalized(n) << "\n";);
        if (reflect(n))
            for (expr* arg : *n)
                if (!ctx().e_internalized(arg))
                    th.ensure_enode(arg);
        if (ctx().e_internalized(n)) {
            return get_enode(n);
        }
        else {
            return ctx().mk_enode(n, !reflect(n), false, enable_cgc_for(n));       
        }
    }

    bool enable_cgc_for(app * n) const {
        // Congruence closure is not enabled for (+ ...) and (* ...) applications.
        return !(n->get_family_id() == get_id() && (n->get_decl_kind() == OP_ADD || n->get_decl_kind() == OP_MUL));
    }


    void mk_clause(literal l1, literal l2, unsigned num_params, parameter * params) {
        TRACE("arith", literal lits[2]; lits[0] = l1; lits[1] = l2; ctx().display_literals_verbose(tout, 2, lits); tout << "\n";);
        ctx().mk_th_axiom(get_id(), l1, l2, num_params, params);
    }

    void mk_clause(literal l1, literal l2, literal l3, unsigned num_params, parameter * params) {
        TRACE("arith", literal lits[3]; lits[0] = l1; lits[1] = l2; lits[2] = l3; ctx().display_literals_smt2(tout, 3, lits); tout << "\n";);
        ctx().mk_th_axiom(get_id(), l1, l2, l3, num_params, params);
    }


    bool reflect(app* n) const {
        return params().m_arith_reflect || a.is_underspecified(n);          
    }

    bool has_var(expr* n) {
        return ctx().e_internalized(n) && th.is_attached_to_var(get_enode(n));
    }

    void reserve_bounds(theory_var v) {
        while (m_bounds.size() <= static_cast<unsigned>(v)) {
            m_bounds.push_back(lp_bounds());
            m_unassigned_bounds.push_back(0);
        }
    }

    theory_var mk_var(expr* n) {
        if (!ctx().e_internalized(n)) 
            ctx().internalize(n, false);                
        enode* e = get_enode(n);
        theory_var v;
        if (th.is_attached_to_var(e))
            v = e->get_th_var(get_id());
        else {
            v = th.mk_var(e);
            SASSERT(m_bounds.size() <= static_cast<unsigned>(v) || m_bounds[v].empty());
            reserve_bounds(v);
            ctx().attach_th_var(e, &th, v);
        }
        SASSERT(null_theory_var != v);
        return v;
    }

    bool has_int() const { return lp().has_int_var(); }
    
    lpvar register_theory_var_in_lar_solver(theory_var v) {
        lpvar lpv = lp().external_to_local(v);
        if (lpv != lp::null_lpvar)
            return lpv;
        return lp().add_var(v, is_int(v));
    }
        
    void init_left_side(scoped_internalize_state& st) {
        SASSERT(all_zeros(m_columns));
        svector<theory_var> const& vars = st.vars();
        vector<rational> const& coeffs = st.coeffs();
        for (unsigned i = 0; i < vars.size(); ++i) {
            theory_var var = vars[i];
            rational const& coeff = coeffs[i];
            if (m_columns.size() <= static_cast<unsigned>(var)) 
                m_columns.setx(var, coeff, rational::zero());
            else 
                m_columns[var] += coeff;
        }
        m_left_side.clear();
        // reset the coefficients after they have been used.
        for (unsigned i = 0; i < vars.size(); ++i) {
            theory_var var = vars[i];
            rational const& r = m_columns[var];
            if (!r.is_zero()) {
                m_left_side.push_back({r, register_theory_var_in_lar_solver(var)});
                m_columns[var].reset();                    
            }
        }
        SASSERT(all_zeros(m_columns));
    }
        
    bool all_zeros(vector<rational> const& v) const {
        return all_of(v, [](rational const& r) { return r.is_zero(); });
    }
        
    void add_eq_constraint(lp::constraint_index index, enode* n1, enode* n2) {
        m_constraint_sources.setx(index, equality_source, null_source);
        m_equalities.setx(index, enode_pair(n1, n2), enode_pair(0, 0));
    }
        
    void add_ineq_constraint(lp::constraint_index index, literal lit) {
        m_constraint_sources.setx(index, inequality_source, null_source);
        m_inequalities.setx(index, lit, null_literal);
    }

    void add_def_constraint(lp::constraint_index index) {
        m_constraint_sources.setx(index, definition_source, null_source);
        m_definitions.setx(index, null_theory_var, null_theory_var);
    }
        
    void add_def_constraint(lp::constraint_index index, theory_var v) {
        m_constraint_sources.setx(index, definition_source, null_source);
        m_definitions.setx(index, v, null_theory_var);
    }

    bool is_infeasible() const {
        return lp().get_status() == lp::lp_status::INFEASIBLE;
    }

    vector<rational>     m_fixed_values;
    map<rational, theory_var, rational::hash_proc, rational::eq_proc> m_value2var;
    struct undo_value : public trail {
        imp& s;
        undo_value(imp& s):s(s) {}
        void undo() override {
            s.m_value2var.erase(s.m_fixed_values.back());
            s.m_fixed_values.pop_back();
        }
    };

    void register_fixed_var(theory_var v, rational const& value) {
        if (m_value2var.contains(value)) 
            return;
        m_fixed_values.push_back(value);
        m_value2var.insert(value, v);
        ctx().push_trail(undo_value(*this));
    }

    void add_def_constraint_and_equality(lpvar vi, lp::lconstraint_kind kind,
                                         const rational& bound) {
        lpvar vi_equal;
        lp::constraint_index ci = lp().add_var_bound_check_on_equal(vi, kind, bound, vi_equal);
        add_def_constraint(ci);
        if (vi_equal != lp::null_lpvar) 
            report_equality_of_fixed_vars(vi, vi_equal);
        m_new_def = true;
    }
    
    void internalize_eq(theory_var v1, theory_var v2) {  
        app_ref term(m.mk_fresh_const("eq", a.mk_real()), m);
        scoped_internalize_state st(*this);
        st.vars().push_back(v1);
        st.vars().push_back(v2);        
        st.coeffs().push_back(rational::one());
        st.coeffs().push_back(rational::minus_one());
        theory_var z = internalize_linearized_def(term, st);      
        lpvar vi = register_theory_var_in_lar_solver(z);
        add_def_constraint_and_equality(vi, lp::LE, rational::zero());
        add_def_constraint_and_equality(vi, lp::GE, rational::zero());
        TRACE("arith", 
              tout << "v" << v1 << " = " << "v" << v2 << ": " << pp(v1) << " = " << pp(v2) << "\n");
    }

    void del_bounds(unsigned old_size) {
        for (unsigned i = m_bounds_trail.size(); i-- > old_size; ) {
            unsigned v = m_bounds_trail[i];
            api_bound* b = m_bounds[v].back();
            // del_use_lists(b);
            dealloc(b);
            m_bounds[v].pop_back();                        
        }
        m_bounds_trail.shrink(old_size);
    }

    void updt_unassigned_bounds(theory_var v, int inc) {
        TRACE("arith_verbose", tout << "v" << v << " " << m_unassigned_bounds[v] << " += " << inc << "\n";);
        ctx().push_trail(vector_value_trail<unsigned, false>(m_unassigned_bounds, v));
        m_unassigned_bounds[v] += inc;            
    }
       
    bool is_unit_var(scoped_internalize_state& st) {
        return st.vars().size() == 1 && st.coeffs()[0].is_one();
    }


    theory_var internalize_def(app* term, scoped_internalize_state& st) {
        TRACE("arith", tout << expr_ref(term, m) << "\n";);
        if (ctx().e_internalized(term)) {
            IF_VERBOSE(0, verbose_stream() << "repeated term\n";);
            return mk_var(term);
        }
        linearize_term(term, st);
        if (is_unit_var(st)) {
            return st.vars()[0];
        }
        else {
            theory_var v = mk_var(term);
            SASSERT(null_theory_var != v);
            st.coeffs().resize(st.vars().size() + 1);
            st.coeffs()[st.vars().size()] = rational::minus_one();
            st.vars().push_back(v);
            return v;
        }
    }

    // term - v = 0
    theory_var internalize_def(app* term) {
        scoped_internalize_state st(*this);
        linearize_term(term, st);
        return internalize_linearized_def(term, st);
    }

    lpvar get_lpvar(expr* e) {
        theory_var v = mk_var(e);
        m_solver->register_existing_terms();
        return register_theory_var_in_lar_solver(v);
    }

    lpvar get_lpvar(enode* n)  {
        return get_lpvar(n->get_expr());
    }

    lpvar get_lpvar(theory_var v) const {
        return v == null_theory_var ? lp::null_lpvar : lp().external_to_local(v);
    }

    theory_var internalize_linearized_def(app* term, scoped_internalize_state& st) {
        theory_var v = mk_var(term);
        TRACE("arith_internalize", tout << "v" << v << " " << bpp(term) << "\n";);

        if (is_unit_var(st) && v == st.vars()[0]) 
            return st.vars()[0];

        init_left_side(st);
        lpvar vi = get_lpvar(v);
        
        if (vi == UINT_MAX) {
            if (m_left_side.empty()) {
                vi = lp().add_var(v, a.is_int(term));
                add_def_constraint_and_equality(vi, lp::GE, rational(0));
                add_def_constraint_and_equality(vi, lp::LE, rational(0));
            }
            else {
                vi = lp().add_term(m_left_side, v);
                SASSERT(lp().column_has_term(vi));
                TRACE("arith_verbose", 
                      tout << "v" << v << " := " << mk_pp(term, m) 
                      << " slack: " << vi << " scopes: " << m_scopes.size() << "\n";
                      lp().print_term(lp().get_term(vi), tout) << "\n";);
            }
        }

        return v;
    }
        

public:
    imp(theory_lra& th, ast_manager& m): 
        th(th), m(m), 
        a(m), 
        m_arith_eq_adapter(th, a),            
        m_internalize_head(0),
        m_one_var(UINT_MAX),
        m_zero_var(UINT_MAX),
        m_rone_var(UINT_MAX),
        m_rzero_var(UINT_MAX),
        m_asserted_qhead(0), 
        m_assume_eq_head(0),
        m_num_conflicts(0),
        m_model_eqs(DEFAULT_HASHTABLE_INITIAL_CAPACITY, var_value_hash(*this), var_value_eq(*this)),
        m_solver(nullptr),
        m_resource_limit(*this),
        m_farkas("farkas"),
        m_bp(*this, m_implied_bounds),
        m_bounded_range_idx(0),
        m_bounded_range_lit(null_literal),
        m_bound_terms(m),
        m_bound_predicate(m)
    {
        m_bound_params.push_back(parameter(m_farkas));
        m_bound_params.push_back(parameter(rational(1)));
        m_bound_params.push_back(parameter(rational(1)));

    }
        
    ~imp() {
        del_bounds(0);
        std::for_each(m_internalize_states.begin(), m_internalize_states.end(), delete_proc<internalize_state>());
    }

    lp::lar_solver& lp(){ return *m_solver.get(); }
    const lp::lar_solver& lp() const { return *m_solver.get(); }    
 
    void init() {
        if (m_solver) return;

        m_model_is_initialized = false;
        m_solver = alloc(lp::lar_solver); 
        // initialize 0, 1 variables:
        get_one(true);
        get_one(false);
        get_zero(true);
        get_zero(false);

        lp().updt_params(ctx().get_params());
        lp().settings().set_resource_limit(m_resource_limit);
        lp().settings().bound_propagation() = bound_prop_mode::BP_NONE != propagation_mode();

        // todo : do not use m_arith_branch_cut_ratio for deciding on cheap cuts
        unsigned branch_cut_ratio = ctx().get_fparams().m_arith_branch_cut_ratio;
        lp().set_cut_strategy(branch_cut_ratio);
        
        lp().settings().int_run_gcd_test() = ctx().get_fparams().m_arith_gcd_test;
        lp().settings().set_random_seed(ctx().get_fparams().m_random_seed);
        m_lia = alloc(lp::int_solver, *m_solver.get());
    }
        
    void internalize_is_int(app * n) {
        SASSERT(a.is_is_int(n));
        (void) mk_enode(n);
        if (!ctx().relevancy())
            mk_is_int_axiom(n);        
    }

    bool internalize_atom(app * atom, bool gate_ctx) {
        TRACE("arith_internalize", tout << bpp(atom) << "\n";);
        SASSERT(!ctx().b_internalized(atom));
        expr* n1, *n2;
        rational r;
        lp_api::bound_kind k;
        theory_var v = null_theory_var;
        bool_var bv = ctx().mk_bool_var(atom);
        m_bool_var2bound.erase(bv);
        ctx().set_var_theory(bv, get_id());
        if (a.is_le(atom, n1, n2) && a.is_extended_numeral(n2, r) && is_app(n1)) {
            v = internalize_def(to_app(n1));
            k = lp_api::upper_t;
        }
        else if (a.is_ge(atom, n1, n2) && a.is_extended_numeral(n2, r) && is_app(n1)) {
            v = internalize_def(to_app(n1));
            k = lp_api::lower_t;
        }  
        else if (a.is_le(atom, n1, n2) && a.is_extended_numeral(n1, r) && is_app(n2)) {
            v = internalize_def(to_app(n2));
            k = lp_api::lower_t;
        }
        else if (a.is_ge(atom, n1, n2) && a.is_extended_numeral(n1, r) && is_app(n2)) {
            v = internalize_def(to_app(n2));
            k = lp_api::upper_t;
        }
        else if (a.is_is_int(atom)) {
            internalize_is_int(atom);
            return true;
        }
        else {
            TRACE("arith", tout << "Could not internalize " << mk_pp(atom, m) << "\n";);
            found_unsupported(atom);
            return true;
        }

        if (is_int(v) && !r.is_int()) 
            r = (k == lp_api::upper_t) ? floor(r) : ceil(r);
        
        api_bound* b = mk_var_bound(bv, v, k, r);
        m_bounds[v].push_back(b);
        updt_unassigned_bounds(v, +1);
        m_bounds_trail.push_back(v);
        m_bool_var2bound.insert(bv, b);
        mk_bound_axioms(*b);
        TRACE("arith_internalize", tout << "Internalized " << bv << ": " << bpp(atom) << "\n";);
        return true;
    }
        
    bool internalize_term(app * term) {
        if (ctx().e_internalized(term) && th.is_attached_to_var(ctx().get_enode(term))) {
            // skip
        }
        else {
            internalize_def(term);
        }
        return true;
    }

    bool is_arith(enode* n) {
        return n && n->get_th_var(get_id()) != null_theory_var;
    }
        
    void internalize_eq_eh(app * atom, bool_var) {
        if (!ctx().get_fparams().m_arith_eager_eq_axioms)
            return;
        expr* lhs = nullptr, *rhs = nullptr;
        VERIFY(m.is_eq(atom, lhs, rhs));
        enode * n1 = get_enode(lhs);
        enode * n2 = get_enode(rhs);

        if (is_arith(n1) && is_arith(n2) && n1 != n2) 
            m_arith_eq_adapter.mk_axioms(n1, n2);
    }

    void assign_eh(bool_var v, bool is_true) {
        TRACE("arith", tout << "assign p" << literal(v, !is_true) << ": " << bpp(ctx().bool_var2expr(v)) << "\n";);
        m_asserted_atoms.push_back(delayed_atom(v, is_true));
    }

    lbool get_phase(bool_var v) {
        api_bound* b;
        if (!m_bool_var2bound.find(v, b)) {
            return l_undef;
        }
        lp::lconstraint_kind k = lp::EQ;
        switch (b->get_bound_kind()) {
        case lp_api::lower_t:
            k = lp::GE;
            break;
        case lp_api::upper_t:
            k = lp::LE;
            break;
        default:
            break;
        }         
        auto vi = register_theory_var_in_lar_solver(b->get_var());
        if (vi == lp::null_lpvar) {
            return l_undef;
        }
        return lp().compare_values(vi, k, b->get_value()) ? l_true : l_false;
    }

    void initialize_value(expr* var, expr* value) {
        rational r;
        if (!a.is_numeral(value, r)) {
            IF_VERBOSE(5, verbose_stream() << "numeric constant expected in initialization " << mk_pp(var, m) << " := " << mk_pp(value, m) << "\n");
            return;
        }
        lp().move_lpvar_to_value(get_lpvar(var), r);
    }

    void new_eq_eh(theory_var v1, theory_var v2) {
        TRACE("arith", tout << "eq " << v1 << " == " << v2 << "\n";);
        if (!is_int(v1) && !is_real(v1)) 
            return;
        m_arith_eq_adapter.new_eq_eh(v1, v2);
    }

    bool use_diseqs() const {
        return true;
    }

    void new_diseq_eh(theory_var v1, theory_var v2) {
        TRACE("arith", tout << "v" << v1 << " != " << "v" << v2 << "\n";);
        ++m_stats.m_assert_diseq;
        m_arith_eq_adapter.new_diseq_eh(v1, v2);
    }

    void apply_sort_cnstr(enode* n, sort*) {
        TRACE("arith", tout << "sort constraint: " << pp(n) << "\n";);
#if 0
        if (!th.is_attached_to_var(n)) 
            mk_var(n->get_owner());
#endif
    }

    void push_scope_eh() {
        m_scopes.push_back(scope());
        scope& sc = m_scopes.back();
        sc.m_bounds_lim = m_bounds_trail.size();
        sc.m_asserted_qhead = m_asserted_qhead;
        sc.m_asserted_atoms_lim = m_asserted_atoms.size();
        lp().push();
        if (m_nla)
            m_nla->push();
    }

    void pop_scope_eh(unsigned num_scopes) {
        if (num_scopes == 0) 
            return;
        unsigned old_size = m_scopes.size() - num_scopes;
        del_bounds(m_scopes[old_size].m_bounds_lim);
        m_asserted_atoms.shrink(m_scopes[old_size].m_asserted_atoms_lim);
        m_asserted_qhead = m_scopes[old_size].m_asserted_qhead;
        m_scopes.resize(old_size);            
        lp().pop(num_scopes);
        // VERIFY(l_false != make_feasible());
        m_new_bounds.reset();
        m_bv_to_propagate.reset();
        if (m_nla)
            m_nla->pop(num_scopes);
        TRACE("arith", tout << "num scopes: " << num_scopes << " new scope level: " << m_scopes.size() << "\n";);
    }

    void restart_eh() {
        m_arith_eq_adapter.restart_eh();
#if 1
        // experiment
        if (m_lia) {
            std::function<bool(unsigned)> is_root = [&](unsigned j) {
                theory_var v = lp().local_to_external(j);
                if (v < 0)
                    return false;
                auto* n = get_enode(v);
                if (!th.is_relevant_and_shared(n))
                    return false;
                if (n->is_root())
                    return true;
                theory_var w = n->get_root()->get_th_var(get_id());
                return w == v;
            };
            m_lia->simplify(is_root);
            for (auto const& [i, j, e] : m_lia->equalities())
                add_eq(i, j, e, false);
        }
#endif
        if (m_nla)
            m_nla->simplify();
    }

    void relevant_eh(app* n) {
        expr* n1, *n2;
        if (a.is_mod(n, n1, n2)) 
            mk_idiv_mod_axioms(n1, n2);
        else if (a.is_rem(n, n1, n2))
            mk_rem_axiom(n1, n2);
        else if (a.is_div(n, n1, n2)) 
            mk_div_axiom(n1, n2);
        else if (a.is_to_int(n)) 
            mk_to_int_axiom(n);
        else if (a.is_is_int(n))
            mk_is_int_axiom(n);            
        else if (m.is_ite(n))
            mk_ite_axiom(n);
        else if (a.is_power(n, n1, n2))
            mk_power_axiom(n, n1, n2);
    }

    void mk_power_axiom(expr* p, expr* x, expr* y) {
        rational r;
        // r > 0 => r^y > 0
        if (a.is_extended_numeral(x, r) && r > 0) {
            expr_ref zero(a.mk_real(0), m);
            mk_axiom(~mk_literal(a.mk_le(p, zero)));
        }
        bool can_be_underspecified = false;
        if (a.is_numeral(x, r) && r == 0 && (!a.is_numeral(y, r) || r == 0))
            can_be_underspecified = true;
        if (!a.is_extended_numeral(x, r) && 
            !a.is_extended_numeral(y, r)) 
            can_be_underspecified = true;
        if (can_be_underspecified) {
            literal lit = th.mk_eq(p, a.mk_power0(x, y), false);
            ctx().mark_as_relevant(lit);
            ctx().assign(lit, nullptr);
        }
    }

    //  n < 0 || rem(a, n) =  mod(a, n)
    // !n < 0 || rem(a, n) = -mod(a, n)
    void mk_rem_axiom(expr* dividend, expr* divisor) {
        expr_ref zero(a.mk_int(0), m);
        expr_ref rem(a.mk_rem(dividend, divisor), m);
        expr_ref mod(a.mk_mod(dividend, divisor), m);
        expr_ref mmod(a.mk_uminus(mod), m);
        expr_ref degz_expr(a.mk_ge(divisor, zero), m);
        literal dgez = mk_literal(degz_expr);
        literal pos = th.mk_eq(rem, mod,  false);
        literal neg = th.mk_eq(rem, mmod, false);
        {
            scoped_trace_stream ts(th, ~dgez, pos);
            mk_axiom(~dgez, pos);
        }
        {
            scoped_trace_stream ts(th, dgez, neg);
            mk_axiom( dgez, neg);
        }
    }

    // q = 0 or q * (p div q) = p
    void mk_div_axiom(expr* p, expr* q) {
        if (a.is_zero(q)) return;
        literal eqz = th.mk_eq(q, a.mk_real(0), false);
        literal eq  = th.mk_eq(a.mk_mul(q, a.mk_div(p, q)), p, false);
        scoped_trace_stream ts(th, eqz, eq);
        mk_axiom(eqz, eq);
    }

    // to_int (to_real x) = x
    // to_real(to_int(x)) <= x < to_real(to_int(x)) + 1
    void mk_to_int_axiom(app* n) {
        expr* x = nullptr, *y = nullptr;
        VERIFY (a.is_to_int(n, x));            
        if (a.is_to_real(x, y)) {
            literal eq = th.mk_eq(y, n, false);
            scoped_trace_stream ts(th, eq);
            mk_axiom(eq);
        }
        else {
            expr_ref to_r(a.mk_to_real(n), m);
            expr_ref lo(a.mk_le(a.mk_sub(to_r, x), a.mk_real(0)), m);
            expr_ref hi(a.mk_ge(a.mk_sub(x, to_r), a.mk_real(1)), m);
            literal llo = mk_literal(lo);
            literal lhi = mk_literal(hi);
            {
                scoped_trace_stream ts(th, llo);
                mk_axiom(llo);
            }
            {
                scoped_trace_stream ts(th, lhi);
                mk_axiom(~lhi);
            }
        }
    }

    void mk_ite_axiom(expr* n) {
        return;
        expr* c = nullptr, *t = nullptr, *e = nullptr;
        VERIFY(m.is_ite(n, c, t, e));
        literal e1 = th.mk_eq(n, t, false);
        literal e2 = th.mk_eq(n, e, false);
        scoped_trace_stream sts(th, e1, e2);
        mk_axiom(e1, e2);
    }

    // is_int(x) <=> to_real(to_int(x)) = x
    void mk_is_int_axiom(app* n) {
        expr* x = nullptr;
        VERIFY(a.is_is_int(n, x));
        literal eq = th.mk_eq(a.mk_to_real(a.mk_to_int(x)), x, false);
        literal is_int = ctx().get_literal(n);
        scoped_trace_stream _sts1(th, ~is_int, eq);
        scoped_trace_stream _sts2(th, is_int, ~eq);
        mk_axiom(~is_int, eq);
        mk_axiom(is_int, ~eq);

    }

    // create axiom for 
    //    u = v + r*w,
    ///   abs(r) > r >= 0
    void assert_idiv_mod_axioms(theory_var u, theory_var v, theory_var w, rational const& r) {
        app_ref term(m);
        term = a.mk_mul(a.mk_numeral(r, true), get_enode(w)->get_expr());
        term = a.mk_add(get_enode(v)->get_expr(), term);
        term = a.mk_sub(get_enode(u)->get_expr(), term);
        theory_var z = internalize_def(term);
        lpvar zi = register_theory_var_in_lar_solver(z);
        lpvar vi = register_theory_var_in_lar_solver(v);
        add_def_constraint_and_equality(zi, lp::GE, rational::zero());
        add_def_constraint_and_equality(zi, lp::LE, rational::zero());
        add_def_constraint_and_equality(vi, lp::GE, rational::zero());
        add_def_constraint_and_equality(vi, lp::LT, abs(r));
        SASSERT(!is_infeasible());
        TRACE("arith", tout << term << "\n" << lp().constraints(););
    }

    void mk_idiv_mod_axioms(expr * p, expr * q) {
        if (a.is_zero(q)) {
            return;
        }
        TRACE("arith", tout << expr_ref(p, m) << " " << expr_ref(q, m) << "\n";);
        // if q is zero, then idiv and mod are uninterpreted functions.
        expr_ref div(a.mk_idiv(p, q), m);
        expr_ref mod(a.mk_mod(p, q), m);
        expr_ref zero(a.mk_int(0), m);
        if (a.is_zero(p)) {
            // q != 0 => (= (div 0 q) 0)
            // q != 0 => (= (mod 0 q) 0)
            literal q_ge_0 = mk_literal(a.mk_ge(q, zero));
            literal q_le_0 = mk_literal(a.mk_le(q, zero));
            literal d_ge_0 = mk_literal(a.mk_ge(div, zero));
            literal d_le_0 = mk_literal(a.mk_le(div, zero));
            literal m_ge_0 = mk_literal(a.mk_ge(mod, zero));
            literal m_le_0 = mk_literal(a.mk_le(mod, zero));
            mk_axiom(q_ge_0, d_ge_0);
            mk_axiom(q_ge_0, d_le_0);
            mk_axiom(q_ge_0, m_ge_0);
            mk_axiom(q_ge_0, m_le_0);
            mk_axiom(q_le_0, d_ge_0);
            mk_axiom(q_le_0, d_le_0);
            mk_axiom(q_le_0, m_ge_0);
            mk_axiom(q_le_0, m_le_0);
            return;
        }
        expr_ref mod_r(a.mk_add(a.mk_mul(q, div), mod), m);
        expr_ref eq_r(th.mk_eq_atom(mod_r, p), m);
        ctx().internalize(eq_r, false);
        literal eq = ctx().get_literal(eq_r);

        rational k(0);
        expr_ref upper(m);

        if (!a.is_numeral(q, k)) 
            ;
        else if (k.is_pos())  
            upper = a.mk_numeral(k - 1, true);
        else if (k.is_neg()) 
            upper = a.mk_numeral(-k - 1, true);

        context& c = ctx();
        if (!k.is_zero()) {
            mk_axiom(eq);
            m_arith_eq_adapter.mk_axioms(th.ensure_enode(mod_r), th.ensure_enode(p));
            mk_axiom(mk_literal(a.mk_ge(mod, zero)));
            mk_axiom(mk_literal(a.mk_le(mod, upper)));
            
            {
                std::function<void(void)> log = [&,this]() {
                    th.log_axiom_unit(m.mk_implies(m.mk_not(m.mk_eq(q, zero)), c.bool_var2expr(eq.var())));
                    th.log_axiom_unit(m.mk_implies(m.mk_not(m.mk_eq(q, zero)), a.mk_ge(mod, zero)));
                    th.log_axiom_unit(m.mk_implies(m.mk_not(m.mk_eq(q, zero)), a.mk_le(mod, upper)));
                };
                if_trace_stream _ts(m, log);
            }
        }
        else {

            expr_ref abs_q(m.mk_ite(a.mk_ge(q, zero), q, a.mk_uminus(q)), m);
            expr_ref mone(a.mk_int(-1), m);
            expr_ref modmq(a.mk_sub(mod, abs_q), m);
            literal eqz = mk_literal(m.mk_eq(q, zero));
            literal mod_ge_0 = mk_literal(a.mk_ge(mod, zero));
            literal mod_lt_q = mk_literal(a.mk_le(modmq, mone));
            
            // q = 0 or p = (p mod q) + q * (p div q)
            // q = 0 or (p mod q) >= 0
            // q = 0 or (p mod q) < abs(q)
            
            mk_axiom(eqz, eq);
            mk_axiom(eqz, mod_ge_0);
            mk_axiom(eqz, mod_lt_q);
            m_arith_eq_adapter.mk_axioms(th.ensure_enode(mod_r), th.ensure_enode(p));

            if (a.is_zero(p)) {
                mk_axiom(eqz, mk_literal(m.mk_eq(div, zero)));
                mk_axiom(eqz, mk_literal(m.mk_eq(mod, zero)));
            }
            // (or (= y 0)  (<= (* y (div x y)) x))
            else if (!a.is_numeral(q)) {
                expr_ref div_ge(m);
                div_ge = a.mk_ge(a.mk_sub(p, a.mk_mul(q, div)), zero);
                ctx().get_rewriter()(div_ge);
                mk_axiom(eqz, mk_literal(div_ge));
                TRACE("arith", tout << eqz << " " << div_ge << "\n");
            }


#if 0
            
            /*literal div_ge_0   = */ mk_literal(a.mk_ge(div, zero));
            /*literal div_le_0   = */ mk_literal(a.mk_le(div, zero));
            /*literal p_ge_0     = */ mk_literal(a.mk_ge(p, zero));
            /*literal p_le_0     = */ mk_literal(a.mk_le(p, zero));

            // q >= 0 or p = (p mod q) + q * (p div q)
            // q <= 0 or p = (p mod q) + q * (p div q)
            // q >= 0 or (p mod q) >= 0
            // q <= 0 or (p mod q) >= 0
            // q <= 0 or (p mod q) <  q
            // q >= 0 or (p mod q) < -q            
            literal q_ge_0 = mk_literal(a.mk_ge(q, zero));
            literal q_le_0 = mk_literal(a.mk_le(q, zero));
            literal mod_ge_0 = mk_literal(a.mk_ge(mod, zero));

            mk_axiom(q_ge_0, eq);
            mk_axiom(q_le_0, eq);
            mk_axiom(q_ge_0, mod_ge_0);
            mk_axiom(q_le_0, mod_ge_0);
            mk_axiom(q_le_0, ~mk_literal(a.mk_ge(a.mk_sub(mod, q), zero)));            
            mk_axiom(q_ge_0, ~mk_literal(a.mk_ge(a.mk_add(mod, q), zero)));        
#endif

#if 0
            // seem expensive
            
            mk_axiom(q_le_0, ~p_ge_0, div_ge_0); 
            mk_axiom(q_le_0, ~p_le_0, div_le_0); 
            mk_axiom(q_ge_0, ~p_ge_0, div_le_0);             
            mk_axiom(q_ge_0, ~p_le_0, div_ge_0);

            mk_axiom(q_le_0, p_ge_0, ~div_ge_0); 
            mk_axiom(q_le_0, p_le_0, ~div_le_0); 
            mk_axiom(q_ge_0, p_ge_0, ~div_le_0);             
            mk_axiom(q_ge_0, p_le_0, ~div_ge_0);
#endif
 
#if 0
            std::function<void(void)> log = [&,this]() {
                th.log_axiom_unit(m.mk_implies(m.mk_not(m.mk_eq(q, zero)), c.bool_var2expr(eq.var()))); 
                th.log_axiom_unit(m.mk_implies(m.mk_not(m.mk_eq(q, zero)), c.bool_var2expr(mod_ge_0.var()))); 
                th.log_axiom_unit(m.mk_implies(a.mk_lt(q, zero), a.mk_lt(a.mk_sub(mod, q), zero)));
                th.log_axiom_unit(m.mk_implies(a.mk_lt(q, zero), a.mk_lt(a.mk_add(mod, q), zero)));
            };
            if_trace_stream _ts(m, log);
#endif
#if 0
                th.log_axiom_unit(m.mk_implies(m.mk_and(a.mk_gt(q, zero), c.bool_var2expr(p_ge_0.var())), c.bool_var2expr(div_ge_0.var())));
                th.log_axiom_unit(m.mk_implies(m.mk_and(a.mk_gt(q, zero), c.bool_var2expr(p_le_0.var())), c.bool_var2expr(div_le_0.var())));
                th.log_axiom_unit(m.mk_implies(m.mk_and(a.mk_lt(q, zero), c.bool_var2expr(p_ge_0.var())), c.bool_var2expr(div_le_0.var())));
                th.log_axiom_unit(m.mk_implies(m.mk_and(a.mk_lt(q, zero), c.bool_var2expr(p_le_0.var())), c.bool_var2expr(div_ge_0.var())));
#endif
        }
        if (params().m_arith_enum_const_mod && k.is_pos() && k < rational(8)) {
            unsigned _k = k.get_unsigned();
            literal_buffer lits;
            expr_ref_vector exprs(m);
            for (unsigned j = 0; j < _k; ++j) {
                literal mod_j = th.mk_eq(mod, a.mk_int(j), false);
                lits.push_back(mod_j);
                exprs.push_back(c.bool_var2expr(mod_j.var()));
                ctx().mark_as_relevant(mod_j);
            }
            scoped_trace_stream _st(th, lits);
            ctx().mk_th_axiom(get_id(), lits.size(), lits.begin());                
        }            
    }

    void mk_axiom(literal l) {
        ctx().mk_th_axiom(get_id(), false_literal, l);
        if (ctx().relevancy()) {
            ctx().mark_as_relevant(l);
        }
    }

    void mk_axiom(literal l1, literal l2) {
        if (l1 == false_literal) {
            mk_axiom(l2);
            return;
        }
        mk_clause(l1, l2, 0, nullptr);
        if (ctx().relevancy()) {
            ctx().mark_as_relevant(l1);
            ctx().add_rel_watch(~l1, ctx().bool_var2expr(l2.var())); // mark consequent as relevant if antecedent is false.
        }
    }

    void mk_axiom(literal l1, literal l2, literal l3) {
        mk_clause(l1, l2, l3, 0, nullptr);
        if (ctx().relevancy()) {
            ctx().mark_as_relevant(l1);
            ctx().mark_as_relevant(l2);
            ctx().mark_as_relevant(l3);
        }
    }

    literal mk_literal(expr* e) {
        expr_ref pinned(e, m);
        TRACE("mk_bool_var", tout << pinned << " " << pinned->get_id() << "\n";);
        if (!ctx().e_internalized(e)) {
            ctx().internalize(e, false);
        }
        return ctx().get_literal(e);
    }


    void init_search_eh() {
        m_arith_eq_adapter.init_search_eh();
        m_num_conflicts = 0;
    }

    bool can_get_value(theory_var v) const {
        return is_registered_var(v) && m_model_is_initialized;
    }

    bool is_registered_var(theory_var v) const {
        return v != null_theory_var && lp().external_is_used(v);
    }

    void ensure_column(enode* n) {
        ensure_column(n->get_th_var(get_id()));
    }

    void ensure_column(theory_var v) {
        if (!lp().external_is_used(v) && v != null_theory_var) 
            register_theory_var_in_lar_solver(v);
    }

    mutable vector<std::pair<lp::lpvar, rational>> m_todo_terms;

    lp::impq get_ivalue(theory_var v) const {
        SASSERT(is_registered_var(v));       
        return lp().get_column_value(get_lpvar(v));
    }
        
    rational get_value(theory_var v) const {
        return is_registered_var(v) ? lp().get_value(get_lpvar(v)) : rational::zero();        
    }    

    bool m_model_is_initialized{ false };
    
    void init_variable_values() {
        m_model_is_initialized = false;
        if (m.inc() && m_solver.get() && th.get_num_vars() > 0) {   
            ctx().push_trail(value_trail<bool>(m_model_is_initialized));
            m_model_is_initialized = lp().init_model();
            TRACE("arith", display(tout << "update variable values " << m_model_is_initialized << "\n"););            
        }
    }
    
    void random_update() {
        if (m_nla && m_nla->need_check())
            return;
        m_tmp_var_set.reset();
        m_model_eqs.reset();
        svector<lpvar> vars;
        theory_var sz = static_cast<theory_var>(th.get_num_vars());
        for (theory_var v = 0; v < sz; ++v) {
            enode * n1 = get_enode(v);
            if (!th.is_relevant_and_shared(n1)) {
                continue;
            }
            ensure_column(v);
            lp::lpvar vj = lp().external_to_local(v);
            SASSERT(vj != lp::null_lpvar);
            theory_var other = m_model_eqs.insert_if_not_there(v);
            if (other == v) {
                continue;
            }
            enode * n2 = get_enode(other);
            if (n1->get_root() == n2->get_root())
                continue;
            if (!lp().column_is_fixed(vj)) {
                vars.push_back(vj);
            }
            else if (!m_tmp_var_set.contains(other) ) {
                lp::lpvar other_j = lp().external_to_local(other);
                if (!lp().column_is_fixed(other_j)) {
                    m_tmp_var_set.insert(other);
                    vars.push_back(other_j);
                }
            } 
        }
        TRACE("arith", 
              for (theory_var v = 0; v < sz; ++v) 
                  if (th.is_relevant_and_shared(get_enode(v)))  
                      tout << "v" << v << " ";
              tout << "\n"; );
        if (!vars.empty()) {
            lp().random_update(vars.size(), vars.data());
        }
    }

    bool assume_eqs() {

        if (delayed_assume_eqs())
            return true;
        
        TRACE("arith_verbose", display(tout););
        random_update();
        m_model_eqs.reset();
        
        theory_var sz = static_cast<theory_var>(th.get_num_vars());            
        unsigned old_sz = m_assume_eq_candidates.size();
        unsigned num_candidates = 0;
        int start = ctx().get_random_value();
        for (theory_var i = 0; i < sz; ++i) {
            theory_var v = (i + start) % sz;
            enode* n1 = get_enode(v);
            if (!th.is_relevant_and_shared(n1))                   
                continue;
            ensure_column(v);
            if (!is_registered_var(v))
                continue;            
            theory_var other = m_model_eqs.insert_if_not_there(v);
            if (other == v) 
                continue;
            enode* n2 = get_enode(other);
            if (n1->get_root() == n2->get_root())
                continue;
            m_assume_eq_candidates.push_back({v, other});
            num_candidates++;            
        }
            
        if (num_candidates > 0) 
            ctx().push_trail(restore_vector(m_assume_eq_candidates, old_sz));

        return delayed_assume_eqs();
    }

    bool delayed_assume_eqs() {
        if (m_assume_eq_head == m_assume_eq_candidates.size())
            return false;
            
        ctx().push_trail(value_trail<unsigned>(m_assume_eq_head));
        while (m_assume_eq_head < m_assume_eq_candidates.size()) {
            auto const [v1, v2] = m_assume_eq_candidates[m_assume_eq_head];
            enode* n1 = get_enode(v1);
            enode* n2 = get_enode(v2);
            m_assume_eq_head++;
            CTRACE("arith", 
                   is_eq(v1, v2) && n1->get_root() != n2->get_root(),
                   tout << "assuming eq: v" << v1 << " = v" << v2 << "\n";);
            if (is_eq(v1, v2) &&  n1->get_root() != n2->get_root() && th.assume_eq(n1, n2)) {
                ++m_stats.m_assume_eqs;
                return true;
            }
        }
        return false;
    }

    bool is_eq(theory_var v1, theory_var v2) {
        if (use_nra_model()) 
            return m_nla->am().eq(nl_value(v1, m_nla->tmp1()), nl_value(v2, m_nla->tmp2()));
        else 
            return get_ivalue(v1) == get_ivalue(v2); 
    }

    bool has_delayed_constraints() const {
        return !m_asserted_atoms.empty();
    }

    final_check_status eval_power(expr* e) {
        expr* x = nullptr, * y = nullptr;
        rational r;
        VERIFY(a.is_power(e, x, y));
        if (a.is_numeral(x, r) && r == 0 && a.is_numeral(y, r) && r == 0)
            return FC_DONE;
        if (!m_nla)
            return FC_GIVEUP;
        switch (m_nla->check_power(get_lpvar(e), get_lpvar(x), get_lpvar(y))) {
        case l_true:
            return FC_DONE;
        case l_false:
            add_lemmas();
            return FC_CONTINUE;
        case l_undef:
            return FC_GIVEUP;
        default:
            break;
        }
        return FC_GIVEUP;
    }

    final_check_status eval_unsupported(expr* e) {
        if (a.is_power(e)) 
            return eval_power(e);        
        if (a.is_power0(e)) 
            return FC_DONE;
        return FC_GIVEUP;
    }
    
    final_check_status final_check_eh() {
        if (propagate_core())
            return FC_CONTINUE;
        m_model_is_initialized = false;
        IF_VERBOSE(12, verbose_stream() << "final-check " << lp().get_status() << "\n");
        lbool is_sat = l_true;
        SASSERT(lp().ax_is_correct());
        if (!lp().is_feasible() || lp().has_changed_columns()) 
            is_sat = make_feasible();
        final_check_status st = FC_DONE;
        bool int_undef = false;
        switch (is_sat) {
        case l_true:
            TRACE("arith", display(tout));            
                
            switch (check_lia()) {
            case FC_DONE:
                break;
            case FC_CONTINUE:
                return FC_CONTINUE;
            case FC_GIVEUP:
                int_undef = true;
                TRACE("arith", tout << "check-lia giveup\n";);
                if (ctx().get_fparams().m_arith_ignore_int)
                    st = FC_CONTINUE;
                break;
            }

            switch (check_nla()) {
            case FC_DONE:
                break;
            case FC_CONTINUE:
                return FC_CONTINUE;
            case FC_GIVEUP:
                TRACE("arith", tout << "check-nra giveup\n";);
                st = FC_GIVEUP;
                break;
            }                        
                        
            if (assume_eqs()) {
                ++m_stats.m_assume_eqs;
                return FC_CONTINUE;
            }

            if (!int_undef && !check_bv_terms())
                return FC_CONTINUE;
            
            for (expr* e : m_not_handled) {
                if (!ctx().is_relevant(e))
                    continue;
                switch (eval_unsupported(e)) {
                case FC_CONTINUE:
                    st = FC_CONTINUE;
                    break;
                case FC_GIVEUP:
                    TRACE("arith", tout << "give up " << mk_pp(e, m) << "\n");
                    if (st != FC_CONTINUE) 
                        st = FC_GIVEUP;
                    break;
                default:
                    break;
                }
                if (st == FC_CONTINUE)
                    break;
            }
            return st;
        case l_false:
            get_infeasibility_explanation_and_set_conflict();
            return FC_CONTINUE;
        case l_undef:
            TRACE("arith", tout << "check feasible is undef\n";);
            return m.inc() ? FC_CONTINUE : FC_GIVEUP;
        default:
            UNREACHABLE();
            break;
        }
        TRACE("arith", tout << "default giveup\n";);
        return FC_GIVEUP;
    }

        // create an eq atom representing "term = offset"
    app_ref mk_eq(lp::lar_term const& term, rational const& offset) {
        u_map<rational> coeffs;
        term2coeffs(term, coeffs);
        bool isint = offset.is_int();
        for (auto const& kv : coeffs) isint &= is_int(kv.m_key) && kv.m_value.is_int();
        app_ref t = coeffs2app(coeffs, rational::zero(), isint);
        app_ref s(a.mk_numeral(offset, isint), m);
        if (s == t) {
            return app_ref(m.mk_true(), m);
        }
        else {
            app_ref atom(m.mk_eq(t, s), m);
            ctx().internalize(atom, true);
            ctx().mark_as_relevant(atom.get());
            return atom;
        }
    }
    // create a bound atom representing term >= k is lower_bound is true, and term <= k if it is false
    expr_ref mk_bound(lp::lar_term const& term, rational const& k, bool lower_bound) {
        rational offset;
        expr_ref t(m);
        return mk_bound(term, k, lower_bound, offset, t);
    }

    expr_ref mk_bound(lp::lar_term const& term, rational const& k, bool lower_bound, rational& offset, expr_ref& t) {
        offset = k;
        u_map<rational> coeffs;
        term2coeffs(term, coeffs);
        bool is_int = true;
        rational lc = denominator(k);
        for (auto const& kv : coeffs) {
            theory_var w = kv.m_key;
            expr* o = get_enode(w)->get_expr();
            is_int = a.is_int(o);
            if (!is_int) break;
            lc = lcm(lc, denominator(kv.m_value));
        }

        // ensure that coefficients are integers when all variables are integers as well.
        if (is_int && !lc.is_one()) {
            SASSERT(lc.is_pos());
            offset *= lc;
            for (auto& kv : coeffs) kv.m_value *= lc;
        }       

        if (is_int) {
            // 3x + 6y >= 5 -> x + 3y >= 5/3, then x + 3y >= 2
            // 3x + 6y <= 5 -> x + 3y <= 1
            rational g = gcd_reduce(coeffs);
            if (!g.is_one()) {
                if (lower_bound) {
                    TRACE("arith", tout << "lower: " << offset << " / " << g << " = " << offset / g << " >= " << ceil(offset / g) << "\n";);
                    offset = ceil(offset / g);
                }
                else {
                    TRACE("arith", tout << "upper: " << offset << " / " << g << " = " << offset / g << " <= " << floor(offset / g) << "\n";);
                    offset = floor(offset / g);
                }
            }
        }
        if (!coeffs.empty() && coeffs.begin()->m_value.is_neg()) {
            offset.neg();
            lower_bound = !lower_bound;
            for (auto& kv : coeffs) kv.m_value.neg();
        }

        // CTRACE("arith", is_int,
        //        lp().print_term(term, tout << "term: ") << "\n";
        //        tout << "offset: " << offset << " gcd: " << g << "\n";);

        expr_ref atom(m);
        t = coeffs2app(coeffs, rational::zero(), is_int);
        if (lower_bound) 
            atom = a.mk_ge(t, a.mk_numeral(offset, is_int));
        else 
            atom = a.mk_le(t, a.mk_numeral(offset, is_int));        

        // ctx().get_rewriter()(atom);
        // Note: it is not safe to rewrite atom because the rewriter can
        // destroy structure, such as (div x 24) >= 0 becomes x >= 0 and the internal variable
        // corresponding to (div x 24) is not constrained.
        TRACE("arith", tout << t << ": " << atom << "\n";
              lp().print_term(term, tout << "bound atom: ") << (lower_bound?" >= ":" <= ") << k << "\n";);
        ctx().internalize(atom, true);
        ctx().mark_as_relevant(atom.get());
        return atom;
    }


    /**
     * n = (div p q)
     *
     * (div p q) * q + (mod p q) = p, (mod p q) >= 0
     *
     * 0 < q => (p/q <= v(p)/v(q) => n <= floor(v(p)/v(q)))
     * 0 < q => (v(p)/v(q) <= p/q => v(p)/v(q) - 1 < n) 
     * 
     */

    bool check_idiv_bounds() {
        if (!m_nla)
            return true;
        m_nla->check_bounded_divisions();
        add_lemmas();
        return m_nla->lemmas().empty();
    }

    expr_ref var2expr(lpvar v) {
        std::ostringstream name;
        name << "v" << lp().local_to_external(v);
        return expr_ref(m.mk_const(symbol(name.str()), a.mk_int()), m);
    }

    expr_ref multerm(rational const& r, expr* e) {
        if (r.is_one()) return expr_ref(e, m);
        return expr_ref(a.mk_mul(a.mk_numeral(r, true), e), m);
    }

    expr_ref term2expr(lp::lar_term const& term) {
        expr_ref t(m);
        expr_ref_vector ts(m);
        for (lp::lar_term::ival p : term) {
            auto ti = p.j();
            if (lp().column_has_term(ti)) {
                ts.push_back(multerm(p.coeff(), term2expr(lp().get_term(ti))));
            }
            else {
                ts.push_back(multerm(p.coeff(), var2expr(ti)));
            }
        }
        if (ts.size() == 1) {
            t = ts.back();
        }
        else {
            t = a.mk_add(ts.size(), ts.data());
        }
        return t;
    }

    expr_ref constraint2fml(lp::constraint_index ci) {
        lp::lar_base_constraint const& c = lp().constraints()[ci];
        expr_ref fml(m);
        expr_ref_vector ts(m);
        rational rhs = c.rhs();
        for (auto cv : c.coeffs()) {
            ts.push_back(multerm(cv.first, var2expr(cv.second)));
        }
        switch (c.kind()) {
        case lp::LE: fml = a.mk_le(a.mk_add(ts.size(), ts.data()), a.mk_numeral(rhs, true)); break;
        case lp::LT: fml = a.mk_lt(a.mk_add(ts.size(), ts.data()), a.mk_numeral(rhs, true)); break;
        case lp::GE: fml = a.mk_ge(a.mk_add(ts.size(), ts.data()), a.mk_numeral(rhs, true)); break;
        case lp::GT: fml = a.mk_gt(a.mk_add(ts.size(), ts.data()), a.mk_numeral(rhs, true)); break;
        case lp::EQ: fml = m.mk_eq(a.mk_add(ts.size(), ts.data()), a.mk_numeral(rhs, true)); break;
        case lp::NE:
            SASSERT(false); // unexpected
            break;
        }
        return fml;
    }

    void dump_cut_lemma(std::ostream& out, lp::lar_term const& term, lp::mpq const& k, lp::explanation const& ex, bool upper) {
        lp().print_term(term, out << "bound: "); 
        out << (upper?" <= ":" >= ") << k << "\n";
        for (lp::lar_term::ival p : term) {
            auto ti = p.j();
            out << p.coeff() << " * ";
            if (lp().column_has_term(ti)) {
                lp().print_term(lp().get_term(ti), out) << "\n";
            }
            else {
                out << "v" << lp().local_to_external(ti) << "\n";
            }
        }
        for (auto ev : ex) {
            lp().constraints().display(out << ev.coeff() << ": ", ev.ci());
        }
        expr_ref_vector fmls(m);
        for (auto ev : ex) {
            fmls.push_back(constraint2fml(ev.ci()));
        }        
        expr_ref t(term2expr(term), m);
        if (upper) {
            fmls.push_back(m.mk_not(a.mk_ge(t, a.mk_numeral(k, true))));
        }
        else {
            fmls.push_back(m.mk_not(a.mk_le(t, a.mk_numeral(k, true))));
        }
        ast_pp_util visitor(m);
        visitor.collect(fmls);
        visitor.display_decls(out);
        visitor.display_asserts(out, fmls, true);
        out << "(check-sat)\n";            
    }
    
    final_check_status check_lia() {
        TRACE("arith",);
        if (!m.inc()) {
            TRACE("arith", tout << "canceled\n";);
            return FC_CONTINUE;
        }
        auto cr = m_lia->check(&m_explanation);
        if (cr != lp::lia_move::sat && ctx().get_fparams().m_arith_ignore_int) 
            return FC_GIVEUP;

        switch (cr) {
        case lp::lia_move::sat:
            break;

        case lp::lia_move::branch: {
            TRACE("arith", tout << "branch\n";);
            bool u = m_lia->is_upper();
            auto const & k = m_lia->get_offset();
            rational offset;
            expr_ref t(m);
            expr_ref b = mk_bound(m_lia->get_term(), k, !u, offset, t);
            if (m.has_trace_stream()) {
                app_ref body(m);
                body = m.mk_or(b, m.mk_not(b));
                th.log_axiom_instantiation(body);
                m.trace_stream() << "[end-of-instance]\n";
            }
            IF_VERBOSE(4, verbose_stream() << "branch " << b << "\n";);
            // branch on term >= k + 1
            // branch on term <= k
            // TBD: ctx().force_phase(ctx().get_literal(b));
            // at this point we have a new unassigned atom that the 
            // SAT core assigns a value to
            ++m_stats.m_branch;
            return FC_CONTINUE;
        }
        case lp::lia_move::cut: {
            if (ctx().get_fparams().m_arith_ignore_int) 
                return FC_GIVEUP;
            TRACE("arith", tout << "cut\n";);
            ++m_stats.m_gomory_cuts;
            // m_explanation implies term <= k
            reset_evidence();
            for (auto ev : m_explanation) {
                set_evidence(ev.ci(), m_core, m_eqs);
            }
            // The call mk_bound() can set the m_infeasible_column in lar_solver
            // so the explanation is safer to take before this call.
            expr_ref b = mk_bound(m_lia->get_term(), m_lia->get_offset(), !m_lia->is_upper());
            if (m.has_trace_stream()) {
                th.log_axiom_instantiation(b);
                m.trace_stream() << "[end-of-instance]\n";
            }
            IF_VERBOSE(4, verbose_stream() << "cut " << b << "\n");
            TRACE("arith", dump_cut_lemma(tout, m_lia->get_term(), m_lia->get_offset(), m_explanation, m_lia->is_upper()););
            literal lit(ctx().get_bool_var(b), false);
            TRACE("arith", 
                  ctx().display_lemma_as_smt_problem(tout << "new cut:\n", m_core.size(), m_core.data(), m_eqs.size(), m_eqs.data(), lit);
                  display(tout););
            assign(lit, m_core, m_eqs, m_params);
            return FC_CONTINUE;
        }
        case lp::lia_move::conflict:
            TRACE("arith", tout << "conflict\n";);
            // ex contains unsat core
            set_conflict();
            return FC_CONTINUE;
        case lp::lia_move::undef:
            TRACE("arith", tout << "lia undef\n";);
            return FC_CONTINUE;
        case lp::lia_move::continue_with_check:
            return FC_CONTINUE;
        default:
            UNREACHABLE();
        }
        if (!check_idiv_bounds())
            return FC_CONTINUE;
        
        return FC_DONE;
    }

    nla::lemma m_lemma;

    literal mk_literal(nla::ineq const& ineq) {
        bool is_lower = true, pos = true, is_eq = false;
        switch (ineq.cmp()) {
        case lp::LE: is_lower = false; pos = false;  break;
        case lp::LT: is_lower = true;  pos = true; break;
        case lp::GE: is_lower = true;  pos = false;  break;
        case lp::GT: is_lower = false; pos = true; break;
        case lp::EQ: is_eq = true; pos = false; break;
        case lp::NE: is_eq = true; pos = true; break;
        default: UNREACHABLE();
        }
        TRACE("arith", tout << "is_lower: " << is_lower << " pos " << pos << "\n";);
        expr_ref atom(m);
        // TBD utility: lp::lar_term term = mk_term(ineq.m_poly);
        // then term is used instead of ineq.m_term
        if (is_eq) 
            atom = mk_eq(ineq.term(), ineq.rs());
        else 
            // create term >= 0 (or term <= 0)
            atom = mk_bound(ineq.term(), ineq.rs(), is_lower);
        return literal(ctx().get_bool_var(atom), pos);
    }    

    void false_case_of_check_nla(const nla::lemma & l) {
        m_lemma = l; //todo avoid the copy
        m_explanation = l.expl();
        literal_vector core;
        for (auto const& ineq : m_lemma.ineqs()) {
            auto lit = mk_literal(ineq);
            core.push_back(~lit);
        }
        set_conflict_or_lemma(core, false);
    }

    void assume_literal(nla::ineq const& i) {
        auto lit = mk_literal(i);
        ctx().mark_as_relevant(lit);
        ctx().set_true_first_flag(lit.var());
    }
    
    final_check_status check_nla_continue() {
#if Z3DEBUG
        flet f(lp().validate_blocker(), true);
#endif
        lbool r = m_nla->check();
        switch (r) {
        case l_false:
            add_lemmas();
            return FC_CONTINUE;
        case l_true:
            return FC_DONE;
        default:
            return FC_GIVEUP;
        }
    }

    final_check_status check_nla() {
        if (!m.inc()) {
            TRACE("arith", tout << "canceled\n";);
            return FC_GIVEUP;            
        }
        CTRACE("arith",!m_nla, tout << "no nla\n";);
        if (!m_nla)            
            return FC_DONE;        
        if (!m_nla->need_check()) 
            return FC_DONE;
        return check_nla_continue();
    }

    /**
       \brief We must redefine this method, because theory of arithmetic contains
       underspecified operators such as division by 0.
       (/ a b) is essentially an uninterpreted function when b = 0.
       Thus, 'a' must be considered a shared var if it is the child of an underspecified operator.

       if merge(a / b, x + y) and a / b is root, then x + y become shared and all z + u in equivalence class of x + y.
                      

       TBD: when the set of underspecified subterms is small, compute the shared variables below it.
       Recompute the set if there are merges that invalidate it.
       Use the set to determine if a variable is shared.
    */
    bool is_shared(theory_var v) const {
        if (m_underspecified.empty()) 
            return false;
        enode * n      = get_enode(v);
        enode * r      = n->get_root();
        unsigned usz   = m_underspecified.size();
        TRACE("shared", tout << ctx().get_scope_level() << " " <<  enode_pp(n, ctx()) << " " << v << " underspecified " << usz << " parents " << r->get_num_parents() << "\n";);
        if (r->get_num_parents() > 2*usz) {
            for (unsigned i = 0; i < usz; ++i) {
                app* u = m_underspecified[i];
                unsigned sz = u->get_num_args();
                for (unsigned j = 0; j < sz; ++j) 
                    if (ctx().get_enode(u->get_arg(j))->get_root() == r) 
                        return true;
            }
        }
        else {
            for (enode * parent : r->get_const_parents()) 
                if (a.is_underspecified(parent->get_expr())) 
                    return true;
        }
        return false;
    }

    bool m_new_def = false ;

    bool adaptive() const { return ctx().get_fparams().m_arith_adaptive; }
    double adaptive_assertion_threshold() const { return ctx().get_fparams().m_arith_adaptive_assertion_threshold; }

    bool process_atoms() const {
        if (!adaptive())
            return true;
        unsigned total_conflicts = ctx().get_num_conflicts();
        if (total_conflicts < 10)
            return true;
        double f = static_cast<double>(m_num_conflicts)/static_cast<double>(total_conflicts);
        return f >= adaptive_assertion_threshold();
    }

    bool can_propagate() {
        return process_atoms() && can_propagate_core();
    }
    
    bool can_propagate_core() {
        return m_asserted_atoms.size() > m_asserted_qhead || m_new_def;
    }

    bool propagate() {
        return process_atoms() && propagate_core();        
    }

    bool propagate_core() {
        m_model_is_initialized = false;
        flush_bound_axioms();
        propagate_nla(); 
        if (ctx().inconsistent())
            return true;
        if (!can_propagate_core()) 
            return false;
        
        m_new_def = false;        
        while (m_asserted_qhead < m_asserted_atoms.size() && !ctx().inconsistent() && m.inc()) {
            auto [bv, is_true] = m_asserted_atoms[m_asserted_qhead];
                        
            api_bound* b = nullptr;
            TRACE("arith", tout << "propagate: " << literal(bv, !is_true) << "\n";
                  if (!m_bool_var2bound.contains(bv)) tout << "not found\n");
            if (m_bool_var2bound.find(bv, b) && !assert_bound(bv, is_true, *b)) {
                get_infeasibility_explanation_and_set_conflict();
                return true;
            }
            ++m_asserted_qhead;
        }
        if (ctx().inconsistent()) 
            return true;

        lbool lbl = make_feasible();
        if (!m.inc())
            return true;
        
        switch(lbl) {
        case l_false:
            TRACE("arith", tout << "propagation conflict\n";);
            get_infeasibility_explanation_and_set_conflict();
            break;
        case l_true:
            propagate_bounds_with_lp_solver();
            break;
        case l_undef:
            UNREACHABLE();
            break;
        }
        return true;            
    }

    void propagate_nla() {
        if (m_nla) {
            m_nla->propagate();
            add_lemmas();
            lp().collect_more_rows_for_lp_propagation();
        }
    }

    void add_equality(lpvar j, rational const& k, lp::explanation const& exp) {
        TRACE("arith", tout << "equality " << j << " " << k << "\n");
        theory_var v;
        if (k == 1)
            v = m_one_var;
        else if (k == 0)
            v = m_zero_var;
        else if (!m_value2var.find(k, v))
            return;
        theory_var w = lp().local_to_external(j);
        if (w < 0)
            return;
        lpvar i = register_theory_var_in_lar_solver(v);
        add_eq(i, j, exp, true);
    }

    void add_lemmas() {
        if (m_nla->should_check_feasible()) {
            auto is_sat = make_feasible();
            if (l_false == is_sat) {
                get_infeasibility_explanation_and_set_conflict();
                return;
            }
        }
        for (const nla::ineq& i : m_nla->literals())
            assume_literal(i); 
        for (const nla::lemma & l : m_nla->lemmas()) 
            false_case_of_check_nla(l);
        if (!propagate_eqs())
            return;
        for (auto const& [v, k, e] : m_nla->fixed_equalities())
            add_equality(v, k, e);
        for (auto const& [i, j, e] : m_nla->equalities())
            add_eq(i, j, e, false);
    }

    bool should_propagate() const {
        return bound_prop_mode::BP_NONE != propagation_mode();
    }

    bool should_refine_bounds() const {
        return bound_prop_mode::BP_REFINE == propagation_mode() && ctx().at_search_level();
    }

    void consume(rational const& v, lp::constraint_index j) {
        set_evidence(j, m_core, m_eqs);
        m_explanation.add_pair(j, v);
    }
    
    void propagate_bounds_with_lp_solver() {
        if (!should_propagate()) 
            return;

        m_bp.init();
        lp().propagate_bounds_for_touched_rows(m_bp);

        if (!m.inc()) 
            return;
        if (is_infeasible()) {
            get_infeasibility_explanation_and_set_conflict();
        }
        else {
            for (auto& ib : m_bp.ibounds()) {
                m.inc();
                if (ctx().inconsistent())
                    break;
                propagate_lp_solver_bound(ib);
            }
        }
    }

    bool bound_is_interesting(unsigned vi, lp::lconstraint_kind kind, const rational & bval) const {
        theory_var v = lp().local_to_external(vi);
        if (v == null_theory_var) 
            return false;

        if (should_refine_bounds()) 
            return true;

        if (static_cast<unsigned>(v) < m_bounds.size()) 
            for (api_bound* b : m_bounds[v]) 
                if (ctx().get_assignment(b->get_lit()) == l_undef &&
                    null_literal != is_bound_implied(kind, bval, *b)) 
                    return true;

        return false;
    }

#if 0
    unsigned propagate_lp_solver_bound_dry_run(const lp::implied_bound& be) {
        lpvar vi = be.m_j;
        theory_var v = lp().local_to_external(vi);

        if (v == null_theory_var) 
            return 0;

        TRACE("arith", tout << "v" << v << " " << be.kind() << " " << be.m_bound << "\n";);

        reserve_bounds(v);
            
        if (m_unassigned_bounds[v] == 0 && !should_refine_bounds()) {
            TRACE("arith", tout << "return\n";);
            return 0;
        }
        lp_bounds const& bounds = m_bounds[v];
        bool first = true;
        unsigned count = 0;
        for (unsigned i = 0; i < bounds.size(); ++i) {
            api_bound* b = bounds[i];
            if (ctx().get_assignment(b->get_lit()) != l_undef) 
                continue;
            literal lit = is_bound_implied(be.kind(), be.m_bound, *b);
            if (lit == null_literal) 
                continue;
            TRACE("arith", tout << lit << " bound: " << *b << " first: " << first << "\n";);
            ctx().display_literal_verbose(verbose_stream() << "miss ", lit) << "\n";
            display(verbose_stream());
            TRACE("arith", ctx().display_literal_verbose(tout << "miss ", lit) << "\n");
            exit(0);
            
            ++count;
        }
        return count;
    }
#endif
    
    unsigned propagate_lp_solver_bound(const lp::implied_bound& be) {
        lpvar vi = be.m_j;
        theory_var v = lp().local_to_external(vi);

        if (v == null_theory_var) 
            return 0;

        TRACE("arith", tout << "v" << v << " " << be.kind() << " " << be.m_bound << "\n";);

        reserve_bounds(v);
            
        if (m_unassigned_bounds[v] == 0 && !should_refine_bounds()) {
            TRACE("arith", tout << "return\n";);
            return 0;
        }
        lp_bounds const& bounds = m_bounds[v];
        bool first = true;
        unsigned count = 0;
        for (unsigned i = 0; i < bounds.size(); ++i) {
            api_bound* b = bounds[i];
            if (ctx().get_assignment(b->get_lit()) != l_undef) 
                continue;
            literal lit = is_bound_implied(be.kind(), be.m_bound, *b);
            if (lit == null_literal) 
                continue;
            TRACE("arith", tout << lit << " bound: " << *b << " first: " << first << "\n";);

            ++count;

            lp().settings().stats().m_num_of_implied_bounds ++;
            if (first) {
                first = false;
                reset_evidence();
                m_explanation.clear();
                lp().explain_implied_bound(be, m_bp);
            }
            CTRACE("arith", m_unassigned_bounds[v] == 0, tout << "missed bound\n";);
            updt_unassigned_bounds(v, -1);
            TRACE("arith",
                  ctx().display_literals_verbose(tout, m_core);
                  tout << "\n --> ";
                  ctx().display_literal_verbose(tout, lit);
                  tout << "\n";
                  display_evidence(tout, m_explanation);
                  lp().print_implied_bound(be, tout);
                  );


            DEBUG_CODE(
                for (auto& lit : m_core) {
                    VERIFY(ctx().get_assignment(lit) == l_true);
                });
            ++m_stats.m_bound_propagations1;
            assign(lit, m_core, m_eqs, m_params);      
        }
        
        if (should_refine_bounds() && first) 
            refine_bound(v, be);

        return count;
    }

    void refine_bound(theory_var v, const lp::implied_bound& be) {
        lpvar vi = be.m_j;
        if (lp().column_has_term(vi))
            return;
        expr_ref w(get_enode(v)->get_expr(), m);
        if (a.is_add(w) || a.is_numeral(w) || m.is_ite(w))
            return;
        literal bound = null_literal;
        switch (be.kind()) {
        case lp::LE: 
            if (is_int(v) && (lp().column_has_lower_bound(vi) || !lp().column_has_upper_bound(vi)))
                bound = mk_literal(a.mk_le(w, a.mk_numeral(floor(be.m_bound), a.is_int(w)))); 
            if (is_real(v) && !lp().column_has_upper_bound(vi))
                bound = mk_literal(a.mk_le(w, a.mk_numeral(be.m_bound, a.is_int(w))));                 
            break;
        case lp::GE: 
            if (is_int(v) && (lp().column_has_upper_bound(vi) || !lp().column_has_lower_bound(vi)))
                bound = mk_literal(a.mk_ge(w, a.mk_numeral(ceil(be.m_bound), a.is_int(w)))); 
            if (is_real(v) && !lp().column_has_lower_bound(vi))
                bound = mk_literal(a.mk_ge(w, a.mk_numeral(be.m_bound, a.is_int(w))));                 
            break;
        default: 
            break;
        }
        if (bound == null_literal)
            return;
        if (ctx().get_assignment(bound) == l_true)
            return;
        
        ++m_stats.m_bound_propagations1;
        reset_evidence();
        m_explanation.clear();
        lp().explain_implied_bound(be, m_bp);                       
        ctx().mark_as_relevant(bound);
        assign(bound, m_core, m_eqs, m_params);              
    }

    bool add_eq(lpvar u, lpvar v, lp::explanation const& e, bool is_fixed) {
        if (ctx().inconsistent())
            return false;
        theory_var uv = lp().local_to_external(u); // variables that are returned should have external representations
        theory_var vv = lp().local_to_external(v); // so maybe better to have them already transformed to external form
        if (uv == null_theory_var)
            return false;
        if (vv == null_theory_var)
            return false;
        enode* n1 = get_enode(uv);
        enode* n2 = get_enode(vv);

        TRACE("arith", tout << "add-eq " << pp(n1) << " == " << pp(n2) << "\n";);
        if (n1->get_root() == n2->get_root())
            return false;
        expr* e1 = n1->get_expr();
        expr* e2 = n2->get_expr();
        if (e1->get_sort() != e2->get_sort())
            return false;
        if (!is_fixed && !a.is_numeral(e1) && !a.is_numeral(e2) && (m.is_ite(e1) || m.is_ite(e2))) 
            return false;
        reset_evidence();
        for (auto ev : e) 
            set_evidence(ev.ci(), m_core, m_eqs);
        assign_eq(uv, vv);
        return true;
    }

    literal_vector m_core2;

    void assign(literal lit, literal_vector const& core, svector<enode_pair> const& eqs, vector<parameter> const& ps) {
        if (params().m_arith_validate)
            VERIFY(validate_assign(lit, core, eqs));
        if (core.size() < small_lemma_size() && eqs.empty()) {
            m_core2.reset();
            for (auto const& c : core) {
                m_core2.push_back(~c);
            }
            m_core2.push_back(lit);
            justification * js = nullptr;
            if (proofs_enabled()) {
                js = alloc(theory_lemma_justification, get_id(), ctx(), m_core2.size(), m_core2.data(),
                           ps.size(), ps.data());
            }
            ctx().mk_clause(m_core2.size(), m_core2.data(), js, CLS_TH_LEMMA, nullptr);
        }
        else {
            ctx().assign(
                lit, ctx().mk_justification(
                    ext_theory_propagation_justification(
                        get_id(), ctx(), core.size(), core.data(), 
                        eqs.size(), eqs.data(), lit, ps.size(), ps.data())));            
        }
    }

    literal is_bound_implied(lp::lconstraint_kind k, rational const& value, api_bound const& b) const {
        if ((k == lp::LE || k == lp::LT) && b.get_bound_kind() == lp_api::upper_t && value <= b.get_value()) {
            return b.get_lit();
        }
        if ((k == lp::GE || k == lp::GT) && b.get_bound_kind() == lp_api::lower_t && b.get_value() <= value) {
            return b.get_lit();
        }
        if (k == lp::LE && b.get_bound_kind() == lp_api::lower_t && value < b.get_value()) {
            return ~b.get_lit();
        }
        if (k == lp::LT && b.get_bound_kind() == lp_api::lower_t && value <= b.get_value()) {
            return ~b.get_lit();
        }
        if (k == lp::GE && b.get_bound_kind() == lp_api::upper_t && b.get_value() < value) {
            return ~b.get_lit();
        }
        if (k == lp::GT && b.get_bound_kind() == lp_api::upper_t && b.get_value() <= value) {
            return ~b.get_lit();
        }

        return null_literal;
    }

    bool check_bv_terms() {
        for (app* n : m_bv_terms) {
            if (!check_bv_term(n)) {
                ++m_stats.m_bv_axioms;
                return false;
            }
        }
        return true;
    }


    bool check_bv_term(app* n) {
        unsigned sz = 0;
        expr* _x = nullptr, * _y = nullptr;
        if (!ctx().is_relevant(ctx().get_enode(n)))
            return true;
        expr_ref vx(m), vy(m),vn(m);
        rational valn, valx, valy;
        bool is_int;
        VERIFY(a.is_band(n, sz, _x, _y) || a.is_shl(n, sz, _x, _y) || a.is_ashr(n, sz, _x, _y) || a.is_lshr(n, sz, _x, _y));
        if (!get_value(ctx().get_enode(_x), vx) || !get_value(ctx().get_enode(_y), vy) || !get_value(ctx().get_enode(n), vn)) {
            IF_VERBOSE(2, verbose_stream() << "could not get value of " << mk_pp(n, m) << "\n");
            found_unsupported(n);
            return true;
        }
        if (!a.is_numeral(vn, valn, is_int) || !is_int || !a.is_numeral(vx, valx, is_int) || !is_int || !a.is_numeral(vy, valy, is_int) || !is_int) {
            IF_VERBOSE(2, verbose_stream() << "could not get value of " << mk_pp(n, m) << "\n");
            found_unsupported(n);
            return true;
        }
        rational N = rational::power_of_two(sz);
        valx = mod(valx, N);
        valy = mod(valy, N);
        expr_ref x(a.mk_mod(_x, a.mk_int(N)), m);
        expr_ref y(a.mk_mod(_y, a.mk_int(N)), m);
        SASSERT(0 <= valn && valn < N);
        
        // x mod 2^{i + 1} >= 2^i means the i'th bit is 1.
        auto bitof = [&](expr* x, unsigned i) { 
            expr_ref r(m);
            r = a.mk_ge(a.mk_mod(x, a.mk_int(rational::power_of_two(i+1))), a.mk_int(rational::power_of_two(i)));
            return mk_literal(r);
        };

        if (a.is_band(n)) {
            IF_VERBOSE(2, verbose_stream() << "band: " << mk_bounded_pp(n, m) << " " << valn << " := " << valx << "&" << valy << "\n");
            for (unsigned i = 0; i < sz; ++i) {
                bool xb = valx.get_bit(i);
                bool yb = valy.get_bit(i);
                bool nb = valn.get_bit(i);
                if (xb && yb && !nb)
                    ctx().mk_th_axiom(get_id(), ~bitof(x, i), ~bitof(y, i), bitof(n, i));
                else if (nb && !xb)
                    ctx().mk_th_axiom(get_id(), ~bitof(n, i), bitof(x, i));
                else if (nb && !yb)
                    ctx().mk_th_axiom(get_id(), ~bitof(n, i), bitof(y, i));
                else
                    continue;
                return false;
            }
        }
        if (a.is_shl(n)) {
            SASSERT(valy >= 0);
            if (valy >= sz || valy == 0)
                return true;
            unsigned k = valy.get_unsigned();
            sat::literal eq = th.mk_eq(n, a.mk_mod(a.mk_mul(_x, a.mk_int(rational::power_of_two(k))), a.mk_int(N)), false);
            if (ctx().get_assignment(eq) == l_true)
                return true;            
            ctx().mk_th_axiom(get_id(), ~th.mk_eq(y, a.mk_int(k), false), eq);
            IF_VERBOSE(2, verbose_stream() << "shl: " << mk_bounded_pp(n, m) << " " << valn << " := " << valx << " << " << valy << "\n");
            return false;
        }
        if (a.is_lshr(n)) {
            SASSERT(valy >= 0);
            if (valy >= sz || valy == 0)
                return true;
            unsigned k = valy.get_unsigned();
            sat::literal eq = th.mk_eq(n, a.mk_idiv(x, a.mk_int(rational::power_of_two(k))), false);
            if (ctx().get_assignment(eq) == l_true)
                return true;            
            ctx().mk_th_axiom(get_id(), ~th.mk_eq(y, a.mk_int(k), false), eq);
            IF_VERBOSE(2, verbose_stream() << "lshr: " << mk_bounded_pp(n, m) << " " << valn << " := " << valx << " >>l " << valy << "\n");
            return false;
        }
        if (a.is_ashr(n)) {
            SASSERT(valy >= 0);
            if (valy >= sz || valy == 0)
                return true;
            unsigned k = valy.get_unsigned();
            sat::literal signx = mk_literal(a.mk_ge(x, a.mk_int(N/2)));
            sat::literal eq;
            expr* xdiv2k;
            switch (ctx().get_assignment(signx)) {
            case l_true:
                // x < 0 & y = k -> n = (x div 2^k - 2^{N-k}) mod 2^N
                xdiv2k = a.mk_idiv(x, a.mk_int(rational::power_of_two(k)));
                eq = th.mk_eq(n, a.mk_mod(a.mk_add(xdiv2k, a.mk_int(-rational::power_of_two(sz - k))), a.mk_int(N)), false);
                if (ctx().get_assignment(eq) == l_true)
                    return true;
                break;
            case l_false:
                // x >= 0 & y = k -> n = x div 2^k
                xdiv2k = a.mk_idiv(x, a.mk_int(rational::power_of_two(k)));
                eq = th.mk_eq(n, xdiv2k, false);
                if (ctx().get_assignment(eq) == l_true)
                    return true;
                break;
            case l_undef:
                ctx().mark_as_relevant(signx);
                return false;
            }
            ctx().mk_th_axiom(get_id(), ~th.mk_eq(y, a.mk_int(k), false), ~signx, eq); 
            return false;
        }
        return true;
    }

    expr_ref mk_le(expr* x, expr* y) {
        if (a.is_numeral(y))
            return expr_ref(a.mk_le(x, y), m);
        if (a.is_numeral(x))
            return expr_ref(a.mk_ge(y, x), m);
        return expr_ref(a.mk_le(a.mk_sub(x, y), a.mk_numeral(rational(0), x->get_sort())), m);
    }

    void mk_bv_axiom(app* n) {
        unsigned sz = 0;
        expr* _x = nullptr, * _y = nullptr;
        VERIFY(a.is_band(n, sz, _x, _y) || a.is_shl(n, sz, _x, _y) || a.is_ashr(n, sz, _x, _y) || a.is_lshr(n, sz, _x, _y));
        rational N = rational::power_of_two(sz);
        expr_ref x(a.mk_mod(_x, a.mk_int(N)), m);
        expr_ref y(a.mk_mod(_y, a.mk_int(N)), m);

        // 0 <= n < 2^sz
        
        ctx().mk_th_axiom(get_id(), mk_literal(a.mk_ge(n, a.mk_int(0))));
        ctx().mk_th_axiom(get_id(), mk_literal(a.mk_le(n, a.mk_int(N - 1))));

        if (a.is_band(n)) {
                       
            // x&y <= x
            // x&y <= y
            // TODO? x = y => x&y = x

            ctx().mk_th_axiom(get_id(), mk_literal(mk_le(n, x)));
            ctx().mk_th_axiom(get_id(), mk_literal(mk_le(n, y)));
        }
        else if (a.is_shl(n)) {
            // y >= sz => n = 0
            // y = 0 => n = x
            ctx().mk_th_axiom(get_id(), ~mk_literal(a.mk_ge(y, a.mk_int(sz))), mk_literal(m.mk_eq(n, a.mk_int(0))));
            ctx().mk_th_axiom(get_id(), ~mk_literal(a.mk_eq(y, a.mk_int(0))), mk_literal(m.mk_eq(n, x)));
        }
        else if (a.is_lshr(n)) {
            // y >= sz => n = 0
            // y = 0 => n = x
            ctx().mk_th_axiom(get_id(), ~mk_literal(a.mk_ge(y, a.mk_int(sz))), mk_literal(m.mk_eq(n, a.mk_int(0))));
            ctx().mk_th_axiom(get_id(), ~mk_literal(a.mk_eq(y, a.mk_int(0))), mk_literal(m.mk_eq(n, x)));
        }
        else if (a.is_ashr(n)) {
            // y >= sz & x < 2^{sz-1} => n = 0
            // y >= sz & x >= 2^{sz-1} => n = -1
            // y = 0 => n = x
            auto signx = mk_literal(a.mk_ge(x, a.mk_int(N/2)));
            ctx().mk_th_axiom(get_id(), ~mk_literal(a.mk_ge(a.mk_mod(y, a.mk_int(N)), a.mk_int(sz))), signx, mk_literal(m.mk_eq(n, a.mk_int(0))));
            ctx().mk_th_axiom(get_id(), ~mk_literal(a.mk_ge(a.mk_mod(y, a.mk_int(N)), a.mk_int(sz))), ~signx, mk_literal(m.mk_eq(n, a.mk_int(N-1))));
            ctx().mk_th_axiom(get_id(), ~mk_literal(a.mk_eq(a.mk_mod(y, a.mk_int(N)), a.mk_int(0))), mk_literal(m.mk_eq(n, x)));            
        }
        else
            UNREACHABLE();
    }


    void mk_bound_axioms(api_bound& b) {
        if (!ctx().is_searching()) {
            //
            // NB. We make an assumption that user push calls propagation 
            // before internal scopes are pushed. This flushes all newly 
            // asserted atoms into the right context.
            //
            m_new_bounds.push_back(&b);
            return;
        }
        theory_var v = b.get_var();
        lp_api::bound_kind kind1 = b.get_bound_kind();
        rational const& k1 = b.get_value();
        lp_bounds & bounds = m_bounds[v];

        api_bound* end = nullptr;
        api_bound* lo_inf = end, *lo_sup = end;
        api_bound* hi_inf = end, *hi_sup = end;
            
        for (api_bound* other : bounds) {
            if (other == &b) continue;
            if (b.get_lit() == other->get_lit()) continue;
            lp_api::bound_kind kind2 = other->get_bound_kind();
            rational const& k2 = other->get_value();
            if (k1 == k2 && kind1 == kind2) {
                // the bounds are equivalent.
                continue;
            }

            SASSERT(k1 != k2 || kind1 != kind2);
            if (kind2 == lp_api::lower_t) {
                if (k2 < k1) {
                    if (lo_inf == end || k2 > lo_inf->get_value()) {
                        lo_inf = other;
                    }
                }
                else if (lo_sup == end || k2 < lo_sup->get_value()) {
                    lo_sup = other;
                }
            }
            else if (k2 < k1) {
                if (hi_inf == end || k2 > hi_inf->get_value()) {
                    hi_inf = other;
                }
            }
            else if (hi_sup == end || k2 < hi_sup->get_value()) {
                hi_sup = other;
            }
        }        
        if (lo_inf != end) mk_bound_axiom(b, *lo_inf);
        if (lo_sup != end) mk_bound_axiom(b, *lo_sup);
        if (hi_inf != end) mk_bound_axiom(b, *hi_inf);
        if (hi_sup != end) mk_bound_axiom(b, *hi_sup);
    }


    void mk_bound_axiom(api_bound& b1, api_bound& b2) {
        literal   l1 = b1.get_lit();
        literal   l2 = b2.get_lit();
        rational const& k1 = b1.get_value();
        rational const& k2 = b2.get_value();
        lp_api::bound_kind kind1 = b1.get_bound_kind();
        lp_api::bound_kind kind2 = b2.get_bound_kind();
        bool v_is_int = b1.is_int();
        SASSERT(b1.get_var() == b2.get_var());
        if (k1 == k2 && kind1 == kind2) return;
        SASSERT(k1 != k2 || kind1 != kind2);
        parameter coeffs[3] = { parameter(symbol("farkas")), 
                                parameter(rational(1)), parameter(rational(1)) };
            
        if (kind1 == lp_api::lower_t) {
            if (kind2 == lp_api::lower_t) {
                if (k2 <= k1) {
                    mk_clause(~l1, l2, 3, coeffs);
                }
                else {
                    mk_clause(l1, ~l2, 3, coeffs);
                }
            }
            else if (k1 <= k2) {
                // k1 <= k2, k1 <= x or x <= k2
                mk_clause(l1, l2, 3, coeffs);
            }
            else {
                // k1 > hi_inf, k1 <= x => ~(x <= hi_inf)
                mk_clause(~l1, ~l2, 3, coeffs);
                if (v_is_int && k1 == k2 + rational(1)) {
                    // k1 <= x or x <= k1-1
                    mk_clause(l1, l2, 3, coeffs);
                }
            }
        }
        else if (kind2 == lp_api::lower_t) {
            if (k1 >= k2) {
                // k1 >= lo_inf, k1 >= x or lo_inf <= x
                mk_clause(l1, l2, 3, coeffs);
            }
            else {
                // k1 < k2, k2 <= x => ~(x <= k1)
                mk_clause(~l1, ~l2, 3, coeffs); 
                if (v_is_int && k1 == k2 - rational(1)) {
                    // x <= k1 or k1+l <= x
                    mk_clause(l1, l2, 3, coeffs);
                }
                    
            }
        }
        else {
            // kind1 == A_UPPER, kind2 == A_UPPER
            if (k1 >= k2) {
                // k1 >= k2, x <= k2 => x <= k1
                mk_clause(l1, ~l2, 3, coeffs);
            }
            else {
                // k1 <= hi_sup , x <= k1 =>  x <= hi_sup
                mk_clause(~l1, l2, 3, coeffs);
            }
        }        
    }

    typedef lp_bounds::iterator iterator;

    void flush_bound_axioms() {
        
        CTRACE("arith", !m_new_bounds.empty(), tout << "flush bound axioms\n";);

        while (!m_new_bounds.empty()) {
            lp_bounds atoms;            
            atoms.push_back(m_new_bounds.back());
            m_new_bounds.pop_back();
            theory_var v = atoms.back()->get_var();
            for (unsigned i = 0; i < m_new_bounds.size(); ++i) {
                if (m_new_bounds[i]->get_var() == v) {
                    atoms.push_back(m_new_bounds[i]);
                    m_new_bounds[i] = m_new_bounds.back();
                    m_new_bounds.pop_back();
                    --i;
                }
            }            
            CTRACE("arith", atoms.size() > 1, 
                   for (auto* a : atoms) a->display(tout) << "\n";);
            lp_bounds occs(m_bounds[v]);
            
            std::sort(atoms.begin(), atoms.end(), compare_bounds());
            std::sort(occs.begin(), occs.end(), compare_bounds());
                
            iterator begin1 = occs.begin();
            iterator begin2 = occs.begin();
            iterator end = occs.end();
            begin1 = first(lp_api::lower_t, begin1, end);
            begin2 = first(lp_api::upper_t, begin2, end);
                
            iterator lo_inf = begin1, lo_sup = begin1;
            iterator hi_inf = begin2, hi_sup = begin2;
            bool flo_inf, fhi_inf, flo_sup, fhi_sup;
            ptr_addr_hashtable<api_bound> visited;
            for (unsigned i = 0; i < atoms.size(); ++i) {
                api_bound* a1 = atoms[i];
                iterator lo_inf1 = next_inf(a1, lp_api::lower_t, lo_inf, end, flo_inf);
                iterator hi_inf1 = next_inf(a1, lp_api::upper_t, hi_inf, end, fhi_inf);
                iterator lo_sup1 = next_sup(a1, lp_api::lower_t, lo_sup, end, flo_sup);
                iterator hi_sup1 = next_sup(a1, lp_api::upper_t, hi_sup, end, fhi_sup);
                if (lo_inf1 != end) lo_inf = lo_inf1; 
                if (lo_sup1 != end) lo_sup = lo_sup1; 
                if (hi_inf1 != end) hi_inf = hi_inf1; 
                if (hi_sup1 != end) hi_sup = hi_sup1; 
                if (!flo_inf) lo_inf = end;
                if (!fhi_inf) hi_inf = end;
                if (!flo_sup) lo_sup = end;
                if (!fhi_sup) hi_sup = end;
                visited.insert(a1);
                if (lo_inf1 != end && lo_inf != end && !visited.contains(*lo_inf)) mk_bound_axiom(*a1, **lo_inf);
                if (lo_sup1 != end && lo_sup != end && !visited.contains(*lo_sup)) mk_bound_axiom(*a1, **lo_sup);
                if (hi_inf1 != end && hi_inf != end && !visited.contains(*hi_inf)) mk_bound_axiom(*a1, **hi_inf);
                if (hi_sup1 != end && hi_sup != end && !visited.contains(*hi_sup)) mk_bound_axiom(*a1, **hi_sup);
            }                            
        }
    }

    struct compare_bounds {
        bool operator()(api_bound* a1, api_bound* a2) const { return a1->get_value() < a2->get_value(); }
    };


    lp_bounds::iterator first(
        lp_api::bound_kind kind, 
        iterator it, 
        iterator end) {
        for (; it != end; ++it) {
            api_bound* a = *it;
            if (a->get_bound_kind() == kind) return it;
        }
        return end;
    }

    lp_bounds::iterator next_inf(
        api_bound* a1, 
        lp_api::bound_kind kind, 
        iterator it, 
        iterator end,
        bool& found_compatible) {
        rational const & k1(a1->get_value());
        iterator result = end;
        found_compatible = false;
        for (; it != end; ++it) {
            api_bound * a2 = *it;            
            if (a1 == a2) continue;
            if (a2->get_bound_kind() != kind) continue;
            rational const & k2(a2->get_value());
            found_compatible = true;
            if (k2 <= k1) {
                result = it;
            }
            else {
                break;
            }
        }
        return result;
    }

    lp_bounds::iterator next_sup(
        api_bound* a1, 
        lp_api::bound_kind kind, 
        iterator it, 
        iterator end,
        bool& found_compatible) {
        rational const & k1(a1->get_value());
        found_compatible = false;
        for (; it != end; ++it) {
            api_bound * a2 = *it;            
            if (a1 == a2) continue;
            if (a2->get_bound_kind() != kind) continue;
            rational const & k2(a2->get_value());
            found_compatible = true;
            if (k1 < k2) {
                return it;
            }
        }
        return end;
    }
        
    // for glb lo': lo' < lo:
    //   lo <= x -> lo' <= x 
    //   lo <= x -> ~(x <= lo')
    // for lub hi': hi' > hi
    //   x <= hi -> x <= hi'
    //   x <= hi -> ~(x >= hi')

    void propagate_bound(bool_var bv, bool is_true, api_bound& b) {
        if (bound_prop_mode::BP_NONE == propagation_mode()) {
            return;
        }
        lp_api::bound_kind k = b.get_bound_kind();
        theory_var v = b.get_var();
        inf_rational val = b.get_value(is_true);
        lp_bounds const& bounds = m_bounds[v];
        SASSERT(!bounds.empty());
        if (bounds.size() == 1) return;
        if (m_unassigned_bounds[v] == 0) return;
        bool v_is_int = b.is_int();
        literal lit1(bv, !is_true);
        literal lit2 = null_literal;
        bool find_glb = (is_true == (k == lp_api::lower_t));
        TRACE("arith_verbose", tout << "v" << v << " find_glb: " << find_glb << " is_true: " << is_true << " k: " << k << " is_lower: " << (k == lp_api::lower_t) << "\n";);
        if (find_glb) {
            rational glb;
            api_bound* lb = nullptr;
            for (api_bound* b2 : bounds) {
                if (b2 == &b) continue;
                rational const& val2 = b2->get_value();
                if (((is_true || v_is_int) ? val2 < val : val2 <= val) && (!lb || glb < val2)) {
                    lb = b2;
                    glb = val2;
                }
            }
            if (!lb) return;
            bool sign = lb->get_bound_kind() != lp_api::lower_t;
            lit2 = lb->get_lit();
            if (sign)
                lit2.neg();                
        }
        else {
            rational lub;
            api_bound* ub = nullptr;
            for (api_bound* b2 : bounds) {
                if (b2 == &b) continue;
                rational const& val2 = b2->get_value();
                if (((is_true || v_is_int) ? val < val2 : val <= val2) && (!ub || val2 < lub)) {
                    ub = b2;
                    lub = val2;
                }
            }
            if (!ub) return;
            bool sign = ub->get_bound_kind() != lp_api::upper_t;
            lit2 = ub->get_lit();
            if (sign)
                lit2.neg();
        }
        updt_unassigned_bounds(v, -1);
        ++m_stats.m_bound_propagations2;
        reset_evidence();
        m_core.push_back(lit1);
        TRACE("arith", 
              ctx().display_literals_verbose(tout, m_core);
              ctx().display_literal_verbose(tout << " => ", lit2);
              tout << "\n";);
        assign(lit2, m_core, m_eqs, m_bound_params);
        ++m_stats.m_bounds_propagations;
    }

    svector<lp::lpvar> m_todo_vars;

    void add_use_lists(api_bound* b) {
        theory_var v = b->get_var();
        lpvar vi = register_theory_var_in_lar_solver(v);
        if (!lp().column_has_term(vi)) {
            return;
        }
        m_todo_vars.push_back(vi);
        while (!m_todo_vars.empty()) {
            auto ti = m_todo_vars.back();
            SASSERT(lp().column_has_term(ti));
            m_todo_vars.pop_back();
            lp::lar_term const& term = lp().get_term(ti);
            for (auto p : term) {
                lp::lpvar wi = p.j();
                if (lp().column_has_term(wi)) {
                    m_todo_vars.push_back(wi);
                }
                else {
                    unsigned w = lp().local_to_external(wi);
                    m_use_list.reserve(w + 1, ptr_vector<api_bound>());
                    m_use_list[w].push_back(b);
                }
            }
        }
    }

    void del_use_lists(api_bound* b) {
        theory_var v = b->get_var();
        lpvar vi = get_lpvar(v);
        if (!lp().column_has_term(vi)) {
            return;
        }
        m_todo_vars.push_back(vi);
        while (!m_todo_vars.empty()) {
            auto ti = m_todo_vars.back();
            SASSERT(lp().column_has_term(ti));
            m_todo_vars.pop_back();
            lp::lar_term const& term = lp().get_term(ti);
            for (auto coeff : term) {
                auto wi = coeff.j();
                if (lp().column_has_term(wi)) {
                    m_todo_vars.push_back(wi);
                }
                else {
                    unsigned w = lp().local_to_external(wi);
                    SASSERT(m_use_list[w].back() == b);
                    m_use_list[w].pop_back();
                }
            }
        }
    }

    //
    // propagate bounds to compound terms
    // The idea is that if bounds on all variables in an inequality ax + by + cz >= k
    // have been assigned we may know the truth value of the inequality by using simple
    // bounds propagation.
    // 
    void propagate_bound_compound(bool_var bv, bool is_true, api_bound& b) {
        theory_var v = b.get_var();
        TRACE("arith", tout << pp(v) << "\n";);
        if (static_cast<unsigned>(v) >= m_use_list.size()) {
            return;
        }
        for (auto const& vb : m_use_list[v]) {
            if (ctx().get_assignment(vb->get_lit()) != l_undef) {
                TRACE("arith_verbose", display_bound(tout << "assigned ", *vb) << "\n";);
                continue;
            }
            inf_rational r;
            // x + y
            // x >= 0, y >= 1 -> x + y >= 1
            // x <= 0, y <= 2 -> x + y <= 2
            literal lit = null_literal;
            if (lp_api::lower_t == vb->get_bound_kind()) {
                if (get_glb(*vb, r) && r >= vb->get_value()) {        // vb is assigned true
                    lit = vb->get_lit(); 
                }
                else if (get_lub(*vb, r) && r < vb->get_value()) {    // vb is assigned false
                    lit = ~vb->get_lit();
                }
            }
            else {                     
                if (get_glb(*vb, r) && r > vb->get_value()) {         // VB <= value < val(VB)
                    lit = ~vb->get_lit();
                }
                else if (get_lub(*vb, r) && r <= vb->get_value()) {   // val(VB) <= value
                    lit = vb->get_lit();
                }
            }                
                
            // get_glb and get_lub set m_core, m_eqs, m_params
            if (lit != null_literal) {
                TRACE("arith",
                      ctx().display_literals_verbose(tout, m_core);
                      ctx().display_literal_verbose(tout << "\n --> ", lit) << "\n";
                      );
                

                assign(lit, m_core, m_eqs, m_params);
            }
            else {
                TRACE("arith_verbose", display_bound(tout << "skip ", *vb) << "\n";);
            }
        }
    }

    bool get_lub(api_bound const& b, inf_rational& lub) {
        return get_bound(b, lub, true);
    }

    bool get_glb(api_bound const& b, inf_rational& glb) {
        return get_bound(b, glb, false);
    }

    std::ostream& display_bound(std::ostream& out, api_bound const& b) {
        return out << mk_pp(ctx().bool_var2expr(b.get_lit().var()), m);
    }

    bool get_bound(api_bound const& b, inf_rational& r, bool is_lub) {
        reset_evidence();
        r.reset();
        theory_var v = b.get_var();
        lp::lpvar ti = get_lpvar(v);
        SASSERT(lp().column_has_term(ti));
        lp::lar_term const& term = lp().get_term(ti);
        for (auto const mono : term) {
            auto wi = mono.j();
            u_dependency* ci = nullptr;
            rational value;
            bool is_strict;
            if (lp().column_has_term(wi)) {
                return false;
            }
            if (mono.coeff().is_neg() == is_lub) {
                // -3*x ... <= lub based on lower bound for x.
                if (!lp().has_lower_bound(wi, ci, value, is_strict)) {
                    return false;
                }
                if (is_strict) {
                    r += inf_rational(rational::zero(), mono.coeff().is_pos());
                }
            }
            else {
                if (!lp().has_upper_bound(wi, ci, value, is_strict)) {
                    return false;
                }
                if (is_strict) {
                    r += inf_rational(rational::zero(), mono.coeff().is_pos());
                }
            }                
            r += value * mono.coeff();
            set_evidence(ci, m_core, m_eqs);                    
        }
        TRACE("arith_verbose", tout << (is_lub?"lub":"glb") << " is " << r << "\n";);
        return true;
    }

    lp::lconstraint_kind bound2constraint_kind(bool is_int, lp_api::bound_kind bk, bool is_true) {
        switch (bk) {
        case lp_api::lower_t:
            return is_true ? lp::GE : (is_int ? lp::LE : lp::LT);
        case lp_api::upper_t:
            return is_true ? lp::LE : (is_int ? lp::GE : lp::GT);
        }
        UNREACHABLE();
        return lp::EQ;
    }

    bool assert_bound(bool_var bv, bool is_true, api_bound& b) {
        TRACE("arith", tout << b << "\n";);
        lp::constraint_index ci = b.get_constraint(is_true);
        lp().activate(ci);
        if (is_infeasible()) 
            return false;
        lp::lconstraint_kind k = bound2constraint_kind(b.is_int(), b.get_bound_kind(), is_true);
        if (k == lp::LT || k == lp::LE) {
            ++m_stats.m_assert_lower;
        }
        else {
            ++m_stats.m_assert_upper;
        }
        inf_rational value = b.get_value(is_true);
        if (propagate_eqs() && value.is_rational()) 
            propagate_eqs(b.column_index(), ci, k, b, value.get_rational());
        return true;
#if 0
        if (should_propagate())
            lp().add_column_rows_to_touched_rows(b.tv().id());
#endif
    }

    api_bound* mk_var_bound(bool_var bv, theory_var v, lp_api::bound_kind bk, rational const& bound) {
        scoped_internalize_state st(*this);
        st.vars().push_back(v);
        st.coeffs().push_back(rational::one());
        init_left_side(st);
        lp::constraint_index cT, cF;
        bool v_is_int = is_int(v);
        auto vi = register_theory_var_in_lar_solver(v);

        lp::lconstraint_kind kT = bound2constraint_kind(v_is_int, bk, true);
        lp::lconstraint_kind kF = bound2constraint_kind(v_is_int, bk, false);
        
        cT = lp().mk_var_bound(vi, kT, bound);
        if (v_is_int) {
            rational boundF = (bk == lp_api::lower_t) ? bound - 1 : bound + 1;
            cF = lp().mk_var_bound(vi, kF, boundF);
        }
        else {
            cF = lp().mk_var_bound(vi, kF, bound);
        }
        add_ineq_constraint(cT, literal(bv, false));
        add_ineq_constraint(cF, literal(bv, true));

        return alloc(api_bound, literal(bv, false), v, vi, v_is_int, bound, bk, cT, cF);
    }

    //
    // fixed equalities.
    // A fixed equality is inferred if there are two variables v1, v2 whose
    // upper and lower bounds coincide.
    // Then the equality v1 == v2 is propagated to the core.
    // 

    typedef std::pair<lp::constraint_index, rational> constraint_bound;
    vector<constraint_bound>        m_lower_terms;
    vector<constraint_bound>        m_upper_terms;

    void propagate_eqs(lp::lpvar t, lp::constraint_index ci1, lp::lconstraint_kind k, api_bound& b, rational const& value) {
        u_dependency* ci2 = nullptr;
        auto pair = [&]() { return lp().dep_manager().mk_join(lp().dep_manager().mk_leaf(ci1), ci2);  };
        if (k == lp::GE && set_lower_bound(t, ci1, value) && has_upper_bound(t, ci2, value)) {
            fixed_var_eh(b.get_var(), t, pair(), value);
        }
        else if (k == lp::LE && set_upper_bound(t, ci1, value) && has_lower_bound(t, ci2, value)) {
            fixed_var_eh(b.get_var(), t, pair(), value);
        }
    }


    bool propagate_eqs() const { return params().m_arith_propagate_eqs && m_num_conflicts < params().m_arith_propagation_threshold; }

    bound_prop_mode propagation_mode() const { return m_num_conflicts < params().m_arith_propagation_threshold ? params().m_arith_bound_prop : bound_prop_mode::BP_NONE; }

    unsigned small_lemma_size() const { return params().m_arith_small_lemma_size; }

    bool proofs_enabled() const { return m.proofs_enabled(); }

    bool set_upper_bound(lp::lpvar t, lp::constraint_index ci, rational const& v) { return set_bound(t, ci, v, false);  }

    bool set_lower_bound(lp::lpvar t, lp::constraint_index ci, rational const& v) { return set_bound(t, ci, v, true);   }

    vector<constraint_bound> m_history;

    bool set_bound(lp::lpvar tv, lp::constraint_index ci, rational const& v, bool is_lower) {
        if (lp().column_has_term(tv)) {
            auto& vec = is_lower ? m_lower_terms : m_upper_terms;
            if (vec.size() <= tv) {
                vec.resize(tv + 1, constraint_bound(UINT_MAX, rational()));
            }
            constraint_bound& b = vec[tv];
            if (b.first == UINT_MAX || (is_lower? b.second < v : b.second > v)) {
                TRACE("arith", tout << "tighter bound " << tv << "\n";);
                m_history.push_back(vec[tv]);
                ctx().push_trail(history_trail<constraint_bound>(vec, tv, m_history));
                b.first = ci;
                b.second = v;
            }
            return true;
        }
        else {
            // m_solver already tracks bounds on proper variables, but not on terms.
            bool is_strict = false;
            rational b;
            u_dependency* dep = nullptr;
            if (is_lower) {
                return lp().has_lower_bound(tv, dep, b, is_strict) && !is_strict && b == v;
            }
            else {
                return lp().has_upper_bound(tv, dep, b, is_strict) && !is_strict && b == v;
            }            
        }
    }

    bool var_has_bound(lpvar vi, bool is_lower) {
        bool is_strict = false;
        rational b;
        u_dependency* dep;
        if (is_lower) {
            return lp().has_lower_bound(vi, dep, b, is_strict);
        }
        else {
            return lp().has_upper_bound(vi, dep, b, is_strict);
        }        
    }

    bool has_upper_bound(lpvar vi, u_dependency*& ci, rational const& bound) { return has_bound(vi, ci, bound, false); }

    bool has_lower_bound(lpvar vi, u_dependency*& ci, rational const& bound) { return has_bound(vi, ci, bound, true); }
       
    bool has_bound(lpvar vi, u_dependency*& dep, rational const& bound, bool is_lower) {
        if (lp().column_has_term(vi)) {
            theory_var v = lp().local_to_external(vi);
            rational val;
            TRACE("arith", tout << lp().get_variable_name(vi) << " " << v << "\n";);
            if (v != null_theory_var && a.is_numeral(get_owner(v), val) && bound == val) {
                dep = nullptr;
                return bound == val;
            }

            auto& vec = is_lower ? m_lower_terms : m_upper_terms;
            if (vec.size() > vi) {
                auto const& [ci, coeff] = vec[vi];
                if (ci == UINT_MAX)
                    return false;
                dep = lp().dep_manager().mk_leaf(ci);
                return bound == coeff;
            }
            else {
                return false;
            }
        }
        else {
            bool is_strict = false;
            rational b;
            if (is_lower) {
                return lp().has_lower_bound(vi, dep, b, is_strict) && b == bound && !is_strict;
            }
            else {
                return lp().has_upper_bound(vi, dep, b, is_strict) && b == bound && !is_strict;
            }
        }
    }

    bool is_equal(theory_var x, theory_var y) const { 
        return get_enode(x)->get_root() == get_enode(y)->get_root(); 
    }

    unsigned get_num_vars() const { return th.get_num_vars(); }

    void report_equality_of_fixed_vars(unsigned vi1, unsigned vi2) {
        rational bound(0);
        u_dependency* ci1 = nullptr, *ci2 = nullptr, *ci3 = nullptr, *ci4 = nullptr;
        theory_var v1 = lp().local_to_external(vi1);
        theory_var v2 = lp().local_to_external(vi2);
        TRACE("arith", tout << "fixed: " << pp(v1) << " " << pp(v2) << "\n";);
        // we expect lp() to ensure that none of these returns happen.
        if (is_equal(v1, v2))
            return;
        if (is_int(v1) != is_int(v2))
            return;
        if (!has_lower_bound(vi1, ci1, bound))
            return;
        if (!has_upper_bound(vi1, ci2, bound))
            return;
        if (!has_lower_bound(vi2, ci3, bound))
            return;
        if (!has_upper_bound(vi2, ci4, bound))
            return;
        
        reset_evidence();
        set_evidence(ci1, m_core, m_eqs);
        set_evidence(ci2, m_core, m_eqs);
        set_evidence(ci3, m_core, m_eqs);
        set_evidence(ci4, m_core, m_eqs);
        ++m_stats.m_fixed_eqs;
        assign_eq(v1, v2);
    }

    void assign_eq(theory_var v1, theory_var v2) {
        enode* x = get_enode(v1);
        enode* y = get_enode(v2);
        justification* js = 
            ctx().mk_justification(
                ext_theory_eq_propagation_justification(
                    get_id(), ctx(), m_core.size(), m_core.data(), m_eqs.size(), m_eqs.data(), x, y));
        
        TRACE("arith",
              for (auto c : m_core) 
                  ctx().display_detailed_literal(tout << ctx().get_assign_level(c.var()) << " " << c << " ", c) << "\n";              
              for (auto e : m_eqs) 
                  tout << pp(e.first) << " = " << pp(e.second) << "\n";
              tout << " ==> " << pp(x) << " = " << pp(y) << "\n";
              );
        
        std::function<expr*(void)> fn = [&]() { return m.mk_eq(x->get_expr(), y->get_expr()); };
        scoped_trace_stream _sts(th, fn);

        if (params().m_arith_validate)
            VERIFY(validate_eq(x, y));
        ctx().assign_eq(x, y, eq_justification(js));
    }
    
    void fixed_var_eh(theory_var v, lp::lpvar t, u_dependency* dep, rational const& bound) {
        theory_var w = null_theory_var;
        enode* x = get_enode(v);
        if (m_value2var.find(bound, w)) 
            ;
        else if (bound.is_zero()) 
            w = lp().local_to_external(get_zero(a.is_int(x->get_expr())));
        else if (bound.is_one())
            w = lp().local_to_external(get_one(a.is_int(x->get_expr())));
        else
            return;
        enode* y = get_enode(w);
        TRACE("arith", tout << pp(x) << " == " << pp(y) << "\n");
        if (x->get_sort() != y->get_sort())
            return;
        if (x->get_root() == y->get_root())
            return;
        reset_evidence();
        set_evidence(dep, m_core, m_eqs);
        ++m_stats.m_fixed_eqs;
        assign_eq(v, w);                    
    }

    lbool make_feasible() {
        TRACE("pcs",  tout << lp().constraints(););
        TRACE("arith_verbose", tout << "before calling lp().find_feasible_solution()\n"; display(tout););
        auto status = lp().find_feasible_solution();
        TRACE("arith_verbose", display(tout););
        if (lp().is_feasible())
            return l_true;
        if (status == lp::lp_status::INFEASIBLE)  
            return l_false;
        TRACE("arith", tout << "status treated as inconclusive: " << status << "\n";);
            // TENTATIVE_UNBOUNDED, UNBOUNDED, TENTATIVE_DUAL_UNBOUNDED, DUAL_UNBOUNDED, 
            // TIME_EXAUSTED, EMPTY, UNSTABLE
        return l_undef;
    }
 
    lp::explanation     m_explanation;
    literal_vector      m_core;
    svector<enode_pair> m_eqs;
    vector<parameter>   m_params;

    void reset_evidence() {
        m_core.reset();
        m_eqs.reset();
        m_params.reset();
    }

    // lp::constraint_index const null_constraint_index = UINT_MAX; // not sure what a correct fix is

    void set_evidence(u_dependency* dep, literal_vector& core, svector<enode_pair>& eqs) {
        for (auto ci : lp().flatten(dep))
            set_evidence(ci, core, eqs);
    }

    void set_evidence(lp::constraint_index idx, literal_vector& core, svector<enode_pair>& eqs) {
        if (idx == UINT_MAX) {
            return;
        }
        switch (m_constraint_sources[idx]) {
        case inequality_source: {
            literal lit = m_inequalities[idx];
            SASSERT(lit != null_literal);
            core.push_back(lit);
            break;
        }
        case equality_source: {
            SASSERT(m_equalities[idx].first  != nullptr);
            SASSERT(m_equalities[idx].second != nullptr);
            m_eqs.push_back(m_equalities[idx]);          
            break;
        }
        case definition_source: {
            // skip definitions (these are treated as hard constraints)
            break;
        }
        default:
            UNREACHABLE();
            break;
        }
    }

    void get_infeasibility_explanation_and_set_conflict() {
        m_explanation.clear();
        lp().get_infeasibility_explanation(m_explanation);
        set_conflict();
    }

    void set_conflict() {
        literal_vector core;
        set_conflict_or_lemma(core, true);
    }

    void set_conflict_or_lemma(literal_vector const& core, bool is_conflict) {
        reset_evidence();
        for (literal lit : core) {
            m_core.push_back(lit);
        }
        // lp().shrink_explanation_to_minimum(m_explanation); // todo, enable when perf is fixed
        ++m_num_conflicts;
        ++m_stats.m_conflicts;
        TRACE("arith_conflict",
              tout << "@" << ctx().get_scope_level() << (is_conflict ? " conflict":" lemma");
              for (auto const& p : m_params) tout << " " << p;
              tout << "\n";
              display_evidence(tout << core << " ", m_explanation););
        for (auto ev : m_explanation) 
            set_evidence(ev.ci(), m_core, m_eqs);


        if (params().m_arith_validate)
            VERIFY(validate_conflict(m_core, m_eqs));
        if (is_conflict) {
            ctx().set_conflict(
                ctx().mk_justification(
                    ext_theory_conflict_justification(
                        get_id(), ctx(),  
                        m_core.size(), m_core.data(), 
                        m_eqs.size(), m_eqs.data(), m_params.size(), m_params.data())));
        }
        else {
            for (auto const& eq : m_eqs) {
                m_core.push_back(th.mk_eq(eq.first->get_expr(), eq.second->get_expr(), false));
            }
            for (literal & c : m_core) {
                c.neg();
                ctx().mark_as_relevant(c);
                if (ctx().get_assignment(c) == l_true)
                    return;
            }
            TRACE("arith", ctx().display_literals_verbose(tout, m_core) << "\n";);
            ctx().mk_th_axiom(get_id(), m_core.size(), m_core.data());
        }
    }

    justification * why_is_diseq(theory_var v1, theory_var v2) {
        return nullptr;
    }

    void reset_eh() {
        m_arith_eq_adapter.reset_eh();
        m_solver = nullptr;
        m_internalize_head = 0;
        m_not_handled.reset();
        del_bounds(0);
        m_unassigned_bounds.reset();
        m_asserted_qhead  = 0;
        m_assume_eq_head = 0;
        m_scopes.reset();
        m_stats.reset();
        m_model_is_initialized = false;
    }

    void init_model(model_generator & mg) {
        init_variable_values();
        m_factory = alloc(arith_factory, m);
        mg.register_factory(m_factory);
        if (m_model_is_initialized) {
            expr_ref val(m);
            unsigned nv = th.get_num_vars();
            for (unsigned v = 0; v < nv; ++v) 
                if (get_value(get_enode(v), val))
                    m_factory->register_value(val);

        }
        TRACE("arith", display(tout););
    }

    nlsat::anum const& nl_value(theory_var v, scoped_anum& r) const {
        SASSERT(use_nra_model());
        auto t = get_lpvar(v);
        if (!lp().column_has_term(t))
            m_nla->am().set(r, m_nla->am_value(t));            
        else {

            m_todo_terms.push_back({t, rational::one()});
            TRACE("nl_value", tout << "v" << v << " " << t << "\n";);
            TRACE("nl_value", tout << "v" << v << " := w" << t << "\n";
                  lp().print_term(lp().get_term(t), tout) << "\n";);

            m_nla->am().set(r, 0);
            while (!m_todo_terms.empty()) {
                rational wcoeff = m_todo_terms.back().second;
                t = m_todo_terms.back().first;                
                m_todo_terms.pop_back();
                lp::lar_term const& term = lp().get_term(t);
                TRACE("nl_value", lp().print_term(term, tout) << "\n";);
                scoped_anum r1(m_nla->am());
                rational c1(0);
                m_nla->am().set(r1, c1.to_mpq());
                m_nla->am().add(r, r1, r);                
                for (lp::lar_term::ival arg : term) {
                    auto wi = arg.j();
                    c1 = arg.coeff() * wcoeff;
                    if (lp().column_has_term(wi)) {
                        m_todo_terms.push_back({wi, c1});
                    }
                    else {
                        m_nla->am().set(r1, c1.to_mpq());
                        m_nla->am().mul(m_nla->am_value(wi), r1, r1);
                        m_nla->am().add(r1, r, r);
                    }
                }
            }
        }
        return r;
    }

    model_value_proc * mk_value(enode * n, model_generator & mg) {
        theory_var v = n->get_th_var(get_id());
        expr* o = n->get_expr();
        if (use_nra_model() && lp().external_to_local(v) != lp::null_lpvar) {
            anum const& an = nl_value(v, m_nla->tmp1());
            if (a.is_int(o) && !m_nla->am().is_int(an)) {
                return alloc(expr_wrapper_proc, a.mk_numeral(rational::zero(), a.is_int(o)));
            }
            return alloc(expr_wrapper_proc, a.mk_numeral(m_nla->am(), nl_value(v, m_nla->tmp1()), a.is_int(o)));
        }
        else {
            rational r = get_value(v);
            TRACE("arith", tout << mk_pp(o, m) << " v" << v << " := " << r << "\n";);
            SASSERT("integer variables should have integer values: " && (!a.is_int(o) || r.is_int() || m.limit().is_canceled()));
            if (a.is_int(o) && !r.is_int()) r = floor(r);
            return alloc(expr_wrapper_proc, m_factory->mk_value(r,  o->get_sort()));
        }
    }

    bool get_value(enode* n, rational& val) {
        theory_var v = n->get_th_var(get_id());            
        if (!is_registered_var(v)) return false;
        lpvar vi = get_lpvar(v);
        if (lp().has_value(vi, val)) {
            TRACE("arith", tout << expr_ref(n->get_expr(), m) << " := " << val << "\n";);
            if (is_int(n) && !val.is_int()) return false;
            return true;
        }
        else {
            return false;
        }
    }    

    bool get_value(enode* n, expr_ref& r) {
        rational val;
        if (get_value(n, val)) {
            r = a.mk_numeral(val, is_int(n));
            return true;
        }
        else {
            return false;
        }
    }    

    bool include_func_interp(func_decl* f) {
        return 
            a.is_div0(f) ||
            a.is_idiv0(f) ||
            a.is_power0(f) ||
            a.is_rem0(f) ||
            a.is_mod0(f);        
    }

    bool include_func_interp(enode* n) {
        return include_func_interp(n->get_decl());
    }

    bool get_lower(enode* n, rational& val, bool& is_strict) {
        theory_var v = n->get_th_var(get_id());
        if (!is_registered_var(v)) 
            return false;        
        lpvar vi = get_lpvar(v);
        u_dependency* ci;
        return lp().has_lower_bound(vi, ci, val, is_strict);
    }

    bool get_lower(enode* n, expr_ref& r) {
        bool is_strict;
        rational val;
        if (get_lower(n, val, is_strict) && !is_strict) {
            r = a.mk_numeral(val, is_int(n));
            return true;
        }
        return false;
    }

    bool get_upper(enode* n, rational& val, bool& is_strict) {
        theory_var v = n->get_th_var(get_id());
        if (!is_registered_var(v))
            return false;
        lpvar vi = get_lpvar(v);
        u_dependency* dep = nullptr;
        return lp().has_upper_bound(vi, dep, val, is_strict);
    }

    bool solve_for(enode* n, expr_ref& term) {
        theory_var v = n->get_th_var(get_id());
        if (!is_registered_var(v))
            return false;
        lpvar vi = get_lpvar(v);
        lp::lar_term t;
        rational coeff;
        if (!lp().solve_for(vi, t, coeff))
            return false;
        rational lc(1);
        if (is_int(v)) {
            lc = denominator(coeff);
            for (auto const& cv : t)
                lc = lcm(denominator(cv.coeff()), lc);
            if (lc != 1) {
                coeff *= lc;
                t *= lc;
            }
        }
        term = mk_term(t, is_int(v));
        if (coeff != 0)
            term = a.mk_add(a.mk_numeral(coeff, is_int(v)), term);
        if (lc != 1)
            term = a.mk_idiv(term, a.mk_numeral(lc, true));
        return true;
    }

    bool get_upper(enode* n, expr_ref& r) {
        bool is_strict;
        rational val;
        if (get_upper(n, val, is_strict) && !is_strict) {
            r = a.mk_numeral(val, is_int(n));
            return true;
        }
        return false;
    }

    // Auxiliary verification utilities.

    struct scoped_arith_mode {
        smt_params& p;
        scoped_arith_mode(smt_params& p) : p(p) {
            p.m_arith_mode = arith_solver_id::AS_OLD_ARITH;
        }
        ~scoped_arith_mode() {
            p.m_arith_mode = arith_solver_id::AS_NEW_ARITH;
        }
    };


    bool validate_conflict(literal_vector const& core, svector<enode_pair> const& eqs) {
        if (params().m_arith_mode != arith_solver_id::AS_NEW_ARITH) return true;

        VERIFY(!m_core.empty() || !m_eqs.empty());
        scoped_arith_mode _sa(ctx().get_fparams());
        context nctx(m, ctx().get_fparams(), ctx().get_params());
        add_background(nctx);
        cancel_eh<reslimit> eh(m.limit());
        scoped_timer timer(1000, &eh);
        bool result = l_true != nctx.check();
        CTRACE("arith", !result, ctx().display_lemma_as_smt_problem(tout, core.size(), core.data(), eqs.size(), eqs.data(), false_literal););        
        return result;
    }

    bool validate_assign(literal lit, literal_vector const& core, svector<enode_pair> const& eqs) {
        if (params().m_arith_mode != arith_solver_id::AS_NEW_ARITH) return true;
        scoped_arith_mode _sa(ctx().get_fparams());
        context nctx(m, ctx().get_fparams(), ctx().get_params());
        m_core.push_back(~lit);
        add_background(nctx);
        m_core.pop_back();
        cancel_eh<reslimit> eh(m.limit());
        scoped_timer timer(1000, &eh);
        bool result = l_true != nctx.check();
        CTRACE("arith", !result, ctx().display_lemma_as_smt_problem(tout, core.size(), core.data(), eqs.size(), eqs.data(), lit);
               display(tout););   
        return result;
    }

    bool validate_eq(enode* x, enode* y) {
        static bool s_validating = false;
        if (s_validating)
            return true;
        flet<bool> _svalid(s_validating, true);
        context nctx(m, ctx().get_fparams(), ctx().get_params());
        add_background(nctx);
        expr_ref neq(m.mk_not(m.mk_eq(x->get_expr(), y->get_expr())), m);
        nctx.assert_expr(neq);
        cancel_eh<reslimit> eh(m.limit());
        scoped_timer timer(1000, &eh);
        lbool r = nctx.check();
        if (r == l_true) {
            nctx.display_asserted_formulas(std::cout);
            std::cout.flush();
        }
        return l_true != r;
    }

    void add_background(context& nctx) {
        for (literal c : m_core) {
            expr_ref tmp(m);
            ctx().literal2expr(c, tmp);
            nctx.assert_expr(tmp);
        }
        for (auto const& eq : m_eqs) {
            nctx.assert_expr(m.mk_eq(eq.first->get_expr(), eq.second->get_expr()));
        }
    }        

    theory_lra::inf_eps value(theory_var v) {
        lp::impq ival = get_ivalue(v);
        return inf_eps(rational(0), inf_rational(ival.x, ival.y));
    }

    theory_lra::inf_eps maximize(theory_var v, expr_ref& blocker, bool& has_shared) {
        lp::impq term_max;
        lp::lp_status st;
        lpvar vi = 0;
        if (has_int()) {
            lp().backup_x();
        }
        if (!is_registered_var(v)) {
            TRACE("arith", tout << "cannot get bound for v" << v << "\n";);
            st = lp::lp_status::UNBOUNDED;
        }
        else if (!m.limit().inc()) {
            st = lp::lp_status::UNBOUNDED;
        }
        else {
            if (!lp().is_feasible() || lp().has_changed_columns())
                make_feasible();
            
            vi = get_lpvar(v);
            
            st = lp().maximize_term(vi, term_max);
            if (has_int() && lp().has_inf_int()) {
                st = lp::lp_status::FEASIBLE;
                lp().restore_x();
            }
            if (m_nla && (st == lp::lp_status::OPTIMAL || st == lp::lp_status::UNBOUNDED)) {
                st = lp::lp_status::FEASIBLE;
                lp().restore_x();
            }                
        }
        switch (st) {
        case lp::lp_status::OPTIMAL: {
            init_variable_values();
            TRACE("arith", display(tout << st << " v" << v << " vi: " << vi << "\n"););
            auto val = value(v);
            blocker = mk_gt(v);
            return val;
        }
        case lp::lp_status::FEASIBLE: {
            auto val = value(v);
            TRACE("arith", display(tout << st << " v" << v << " vi: " << vi << "\n"););
            blocker = mk_gt(v);
            return val;
        }
        default:
            SASSERT(st == lp::lp_status::UNBOUNDED);
            TRACE("arith", display(tout << st << " v" << v << " vi: " << vi << "\n"););
            has_shared = false;
            blocker = m.mk_false();
            return inf_eps(rational::one(), inf_rational());
        }
    }

    expr_ref mk_gt(theory_var v) {
        lp::impq val = get_ivalue(v);
        expr* obj = get_enode(v)->get_expr();
        rational r = val.x;
        expr_ref e(m);
        if (a.is_int(obj->get_sort())) {
            if (r.is_int()) 
                r += rational::one();
            else 
                r = ceil(r);
            e = a.mk_numeral(r, obj->get_sort());
            e = a.mk_ge(obj, e);
        }
        else {
            e = a.mk_numeral(r, obj->get_sort());
            if (val.y.is_neg()) 
                e = a.mk_ge(obj, e);
            else 
                e = a.mk_gt(obj, e);
        }
        TRACE("opt", tout << "v" << v << " " << val << " " << r << " " << e << "\n";);
        return e;
    }

    theory_var add_objective(app* term) {
        TRACE("opt", tout << expr_ref(term, m) << "\n";);
        theory_var v = internalize_def(term);
        register_theory_var_in_lar_solver(v);
        return v;
    }

    void term2coeffs(lp::lar_term const& term, u_map<rational>& coeffs) {
        term2coeffs(term, coeffs, rational::one());
    }

    void term2coeffs(lp::lar_term const& term, u_map<rational>& coeffs, rational const& coeff) {
        TRACE("arith", lp().print_term(term, tout) << "\n";);
        for (lp::lar_term::ival ti : term) {
            theory_var w;
            auto tv = ti.j();
            if (lp().column_has_term(tv)) {
                lp::lar_term const& term1 = lp().get_term(tv);
                rational coeff2 = coeff * ti.coeff();
                term2coeffs(term1, coeffs, coeff2);
                continue;
            }
            else {
                w = lp().local_to_external(tv);
                SASSERT(w >= 0);
                TRACE("arith", tout << tv << ": " << w << "\n";);
            }
            rational c0(0);
            coeffs.find(w, c0);
            coeffs.insert(w, c0 + ti.coeff() * coeff);
        }
    }

    app_ref coeffs2app(u_map<rational> const& coeffs, rational const& offset, bool is_int) {
        expr_ref_vector args(m);
        for (auto const& [w, coeff] : coeffs) {
            expr* o = get_enode(w)->get_expr();
            if (coeff.is_zero()) {
                // continue
            }
            else if (coeff.is_one()) {
                args.push_back(o);
            }
            else {
                args.push_back(a.mk_mul(a.mk_numeral(coeff, is_int), o));                
            }
        }
        if (!offset.is_zero()) {
            args.push_back(a.mk_numeral(offset, is_int));
        }
        switch (args.size()) {
        case 0:
            return app_ref(a.mk_numeral(rational::zero(), is_int), m);
        case 1:
            return app_ref(to_app(args[0].get()), m);
        default:
            return app_ref(a.mk_add(args.size(), args.data()), m);
        }
    }

    app_ref mk_term(lp::lar_term const& term, bool is_int) {     
        u_map<rational> coeffs;
        term2coeffs(term, coeffs);
        return coeffs2app(coeffs, rational::zero(), is_int);
    }

    rational gcd_reduce(u_map<rational>& coeffs) {
        rational g(0);
        for (auto const& kv : coeffs) {
            g = gcd(g, kv.m_value);
        }
        if (g.is_zero())
            return rational::one();
        if (!g.is_one()) {
            for (auto& kv : coeffs) {
                kv.m_value /= g;
            }             
        }
        return g;
    }

    app_ref mk_obj(theory_var v) {
        auto t = get_lpvar(v);
        bool is_int = a.is_int(get_enode(v)->get_expr());
        if (lp().column_has_term(t)) {
            return mk_term(lp().get_term(t), is_int);
        }
        else {
            // theory_var w = lp().external_to_local(vi);
            return app_ref(get_enode(v)->get_expr(), m);
        }
    }

    expr_ref mk_ge(generic_model_converter& fm, theory_var v, inf_rational const& val) {
        rational r = val.get_rational();
        bool is_strict =  val.get_infinitesimal().is_pos();
        app_ref b(m);
        bool is_int = a.is_int(get_enode(v)->get_expr());
        TRACE("arith", display(tout << "v" << v << "\n"););
        if (is_strict) {
            b = a.mk_le(mk_obj(v), a.mk_numeral(r, is_int));
        }
        else {
            b = a.mk_ge(mk_obj(v), a.mk_numeral(r, is_int));
        }
        if (!ctx().b_internalized(b)) {
            fm.hide(b->get_decl());
            bool_var bv =  ctx().mk_bool_var(b);
            m_bool_var2bound.erase(bv);
            ctx().set_var_theory(bv, get_id());
            // ctx().set_enode_flag(bv, true);
            lp_api::bound_kind bkind = lp_api::bound_kind::lower_t;
            if (is_strict) bkind = lp_api::bound_kind::upper_t;
            api_bound* a = mk_var_bound(bv, v, bkind, r);
            mk_bound_axioms(*a);
            updt_unassigned_bounds(v, +1);
            m_bounds[v].push_back(a);
            m_bounds_trail.push_back(v);
            m_bool_var2bound.insert(bv, a);

            TRACE("arith", tout << "internalized " << bv << ": " << mk_pp(b, m) << "\n";);
        }
        if (is_strict) {
            b = m.mk_not(b);
        }
        TRACE("arith", tout << b << "\n";);
        return expr_ref(b, m);            
    }


    void display(std::ostream & out) const {
        out << "Theory arithmetic:\n";
        if (m_solver) {
            m_solver->display(out);
        }
        if (m_nla) {
            m_nla->display(out);
        }
        unsigned nv = th.get_num_vars();
        for (unsigned v = 0; v < nv; ++v) {
            auto vi = get_lpvar(v);
            if (!ctx().is_relevant(get_enode(v))) out << "irr: ";
            out << "v" << v << " ";
            if (vi == lp::null_lpvar) out << "null"; else out << (lp().column_has_term(vi) ? "t":"j") << vi;
            if (use_nra_model() && is_registered_var(v)) m_nla->am().display(out << " = ", nl_value(v, m_nla->tmp1()));
            else if (can_get_value(v)) out << " = " << get_value(v); 
            if (is_int(v)) out << ", int";
            if (ctx().is_shared(get_enode(v))) out << ", shared";
            out << " := " << pp(v) << "\n";
        }
    }

    void display_evidence(std::ostream& out, lp::explanation const& evidence) {
        for (auto ev : evidence) {
            expr_ref e(m);
            SASSERT(!ev.coeff().is_zero()); 
            if (ev.coeff().is_zero()) { 
                continue;
            }
            unsigned idx = ev.ci();
            switch (m_constraint_sources.get(idx, null_source)) {
            case inequality_source: {
                literal lit = m_inequalities[idx];
                ctx().literal2expr(lit, e);
                out << bpp(e) << " " << ctx().get_assignment(lit) << "\n";
                break;
            }
            case equality_source: 
                out << pp(m_equalities[idx].first) << " = " 
                    << pp(m_equalities[idx].second) << "\n"; 
                break;
            case definition_source: {
                theory_var v = m_definitions[idx];
                if (v != null_theory_var) 
                    out << "def: v" << v << " := " << pp(th.get_enode(v)) << "\n";
                break;
            }
            case null_source:                    
                out << idx << " null";
                break;
            default:
                UNREACHABLE();
                break; 
            }
        }
        for (lp::explanation::cimpq ev : evidence) 
            lp().constraints().display(out << ev.coeff() << ": ", ev.ci()); 
    }

    void collect_statistics(::statistics & st) const {
        m_arith_eq_adapter.collect_statistics(st);
        m_stats.collect_statistics(st);
        lp().settings().stats().collect_statistics(st);
    }        

    /*
     * Facility to put a small box around integer variables used in branch and bounds.
     */

    unsigned                  m_bounded_range_idx;  // current size of bounded range.
    literal                   m_bounded_range_lit;  // current bounded range literal
    expr_ref_vector           m_bound_terms; // predicates used for bounds
    expr_ref                  m_bound_predicate;

    unsigned init_range() const { return 5; }
    unsigned max_range() const { return 20; }
    

    void setup() {
        m_bounded_range_lit = null_literal;
        m_bound_terms.reset();
        m_bound_predicate = nullptr;
    }


    void validate_model(proto_model& mdl) {

        rational r1, r2;
        expr_ref res(m);
        if (!m_model_is_initialized)
            return;
        for (unsigned v = 0; v < th.get_num_vars(); ++v) {
            if (!is_registered_var(v))
                continue;
            enode* n = get_enode(v);
            if (!n)
                continue;
            if (!th.is_relevant_and_shared(n))
                continue;
            rational r1 = get_value(v);
            if (!mdl.eval(n->get_expr(), res, false))
                continue;
            if (!a.is_numeral(res, r2))
                continue;
            if (r1 != r2)
                IF_VERBOSE(1, verbose_stream() << enode_pp(n, ctx()) << " evaluates to " << r2 << " but arith solver has " << r1 << "\n"); 
        }
    }

};
    
theory_lra::theory_lra(context& ctx):
    theory(ctx, ctx.get_manager().get_family_id("arith")) {
    m_imp = alloc(imp, *this, ctx.get_manager());
}    
theory_lra::~theory_lra() {
    dealloc(m_imp);
}   
theory* theory_lra::mk_fresh(context* new_ctx) {
    return alloc(theory_lra, *new_ctx);
}
void theory_lra::init() {
    m_imp->init();
}    
bool theory_lra::internalize_atom(app * atom, bool gate_ctx) {
    return m_imp->internalize_atom(atom, gate_ctx);
}
bool theory_lra::internalize_term(app * term) {
    return m_imp->internalize_term(term);
}
void theory_lra::internalize_eq_eh(app * atom, bool_var v) {
    m_imp->internalize_eq_eh(atom, v);
}
void theory_lra::assign_eh(bool_var v, bool is_true) {
    m_imp->assign_eh(v, is_true);
}
lbool theory_lra::get_phase(bool_var v) {
    return m_imp->get_phase(v);
}
void theory_lra::initialize_value(expr* var, expr* value) {
    m_imp->initialize_value(var, value);
}
void theory_lra::new_eq_eh(theory_var v1, theory_var v2) {
    m_imp->new_eq_eh(v1, v2);
}
bool theory_lra::use_diseqs() const {
    return m_imp->use_diseqs();
}
void theory_lra::new_diseq_eh(theory_var v1, theory_var v2) {
    m_imp->new_diseq_eh(v1, v2);
}
void theory_lra::apply_sort_cnstr(enode* n, sort* s) {
    m_imp->apply_sort_cnstr(n, s);
}
void theory_lra::push_scope_eh() {
    theory::push_scope_eh();
    m_imp->push_scope_eh();
}
void theory_lra::pop_scope_eh(unsigned num_scopes) {
    m_imp->pop_scope_eh(num_scopes);
    theory::pop_scope_eh(num_scopes);
}
void theory_lra::restart_eh() {
    m_imp->restart_eh();
}
void theory_lra::relevant_eh(app* e) {
    m_imp->relevant_eh(e);
}
void theory_lra::init_search_eh() {
    m_imp->init_search_eh();
}
final_check_status theory_lra::final_check_eh() {
    return m_imp->final_check_eh();
}
bool theory_lra::is_shared(theory_var v) const {
    return m_imp->is_shared(v);
}    
bool theory_lra::can_propagate() {
    return m_imp->can_propagate();
}
void theory_lra::propagate() {
    m_imp->propagate();
}
justification * theory_lra::why_is_diseq(theory_var v1, theory_var v2) {
    return m_imp->why_is_diseq(v1, v2);
}
void theory_lra::reset_eh() {
    m_imp->reset_eh();
}
void theory_lra::init_model(model_generator & m) {
    m_imp->init_model(m);
}
model_value_proc * theory_lra::mk_value(enode * n, model_generator & mg) {
    return m_imp->mk_value(n, mg);
}
bool theory_lra::get_value(enode* n, rational& r) {
    return m_imp->get_value(n, r);
}
bool theory_lra::get_value(enode* n, expr_ref& r) {
    return m_imp->get_value(n, r);
}
bool theory_lra::include_func_interp(func_decl* f) {
    return m_imp->include_func_interp(f);
}
bool theory_lra::get_lower(enode* n, expr_ref& r) {
    return m_imp->get_lower(n, r);
}
bool theory_lra::get_upper(enode* n, expr_ref& r) {
    return m_imp->get_upper(n, r);
}
bool theory_lra::get_lower(enode* n, rational& r, bool& is_strict) {
    return m_imp->get_lower(n, r, is_strict);
}
bool theory_lra::get_upper(enode* n, rational& r, bool& is_strict) {
    return m_imp->get_upper(n, r, is_strict);
}
bool theory_lra::solve_for(enode* n, expr_ref& r) {
    return m_imp->solve_for(n, r);
}

void theory_lra::display(std::ostream & out) const {
    m_imp->display(out);
}
void theory_lra::collect_statistics(::statistics & st) const {
    m_imp->collect_statistics(st);
}
theory_lra::inf_eps theory_lra::value(theory_var v) {
    return m_imp->value(v);
}
theory_lra::inf_eps theory_lra::maximize(theory_var v, expr_ref& blocker, bool& has_shared) {
    return m_imp->maximize(v, blocker, has_shared);
}
theory_var theory_lra::add_objective(app* term) {
    return m_imp->add_objective(term);
}
expr_ref theory_lra::mk_ge(generic_model_converter& fm, theory_var v, inf_rational const& val) {
    return m_imp->mk_ge(fm, v, val);
}

void theory_lra::setup() {
    m_imp->setup();
}

void theory_lra::validate_model(proto_model& mdl) {
    m_imp->validate_model(mdl);
}

}
template  class lp::lp_bound_propagator<smt::theory_lra::imp>;
template void lp::lar_solver::propagate_bounds_for_touched_rows<smt::theory_lra::imp>(lp::lp_bound_propagator<smt::theory_lra::imp>&);
template void lp::lar_solver::check_missed_propagations<smt::theory_lra::imp>(lp::lp_bound_propagator<smt::theory_lra::imp>&);
template void lp::lar_solver::explain_implied_bound<smt::theory_lra::imp>(const lp::implied_bound&, lp::lp_bound_propagator<smt::theory_lra::imp>&);
template unsigned lp::lar_solver::calculate_implied_bounds_for_row<smt::theory_lra::imp>(unsigned int, lp::lp_bound_propagator<smt::theory_lra::imp>&);
