/*
    Copyright (C) 2012, 2013 Fredrik Johansson

    This file is part of FLINT.

    FLINT is free software: you can redistribute it and/or modify it under
    the terms of the GNU Lesser General Public License (LGPL) as published
    by the Free Software Foundation; either version 3 of the License, or
    (at your option) any later version.  See <https://www.gnu.org/licenses/>.
*/

#include "test_helpers.h"
#include "arb.h"

TEST_FUNCTION_START(arb_digamma, state)
{
    slong iter;

    for (iter = 0; iter < 3000 * 0.1 * flint_test_multiplier(); iter++)
    {
        arb_t a, b, c;
        slong prec1, prec2;

        prec1 = 2 + n_randint(state, 1000);
        prec2 = prec1 + 30;

        arb_init(a);
        arb_init(b);
        arb_init(c);

        arb_randtest_precise(a, state, 1 + n_randint(state, 1000), 10);

        arb_digamma(b, a, prec1);
        arb_digamma(c, a, prec2);

        if (!arb_overlaps(b, c))
        {
            flint_printf("FAIL: overlap\n\n");
            flint_printf("a = "); arb_print(a); flint_printf("\n\n");
            flint_printf("b = "); arb_print(b); flint_printf("\n\n");
            flint_printf("c = "); arb_print(c); flint_printf("\n\n");
            flint_abort();
        }

        arb_set(c, a);
        arb_digamma(c, c, prec2);
        if (!arb_overlaps(b, c))
        {
            flint_printf("FAIL: aliasing\n\n");
            flint_printf("a = "); arb_print(a); flint_printf("\n\n");
            flint_printf("b = "); arb_print(b); flint_printf("\n\n");
            flint_printf("c = "); arb_print(c); flint_printf("\n\n");
            flint_abort();
        }

        /* check digamma(z+1) = digamma(z) + 1/z */
        arb_inv(c, a, prec1);
        arb_add(b, b, c, prec1);
        arb_add_ui(c, a, 1, prec1);
        arb_digamma(c, c, prec1);

        if (!arb_overlaps(b, c))
        {
            flint_printf("FAIL: functional equation\n\n");
            flint_printf("a = "); arb_print(a); flint_printf("\n\n");
            flint_printf("b = "); arb_print(b); flint_printf("\n\n");
            flint_printf("c = "); arb_print(c); flint_printf("\n\n");
            flint_abort();
        }

        arb_clear(a);
        arb_clear(b);
        arb_clear(c);
    }

    TEST_FUNCTION_END(state);
}
