[Gauss] Error when computing the rank of a sparse matrix over GF(3) with zero entries #605
Description
Are sparse matrices from the gauss package not allowed to have zero entries? Because I get an error when trying to compute the rank of such a matrix; for example:
LoadPackage("gauss");
SN := SparseMatrix( 2, 3, [ [ 2 ], [ 1, 3 ] ], [ [ 1 ], [ 3, 2 ] ] * One( GF(3) ) );
Rank(SN);
This gives the following error:
┌───────┐ GAP 4.13.0 of 2024-03-15
│ GAP │ https://www.gap-system.org
└───────┘ Architecture: x86_64-pc-linux-gnu-default64-kv9
Configuration: gmp 6.2.1, GASMAN, readline
Loading the library and packages ...
Packages: AClib 1.3.2, Alnuth 3.2.1, AtlasRep 2.1.8, AutPGrp 1.11,
Browse 1.8.21, CaratInterface 2.3.6, CRISP 1.4.6, Cryst 4.1.27,
CrystCat 1.1.10, CTblLib 1.3.9, FactInt 1.6.3, FGA 1.5.0,
Forms 1.2.9, GAPDoc 1.6.7, genss 1.6.8, IO 4.8.2, IRREDSOL 1.4.4,
LAGUNA 3.9.6, orb 4.9.0, Polenta 1.3.10, Polycyclic 2.16,
PrimGrp 3.4.4, RadiRoot 2.9, recog 1.4.2, ResClasses 4.7.3,
SmallGrp 1.5.3, Sophus 1.27, SpinSym 1.5.2, StandardFF 1.0,
TomLib 1.2.11, TransGrp 3.6.5, utils 0.85
Try '??help' for help. See also '?copyright', '?cite' and '?authors'
gap> LoadPackage("gauss");
─────────────────────────────────────────────────────────────────────────────
Loading Gauss 2023.02-04 (Extended Gauss functionality for GAP)
by Simon Görtzen (https://www.linkedin.com/in/simongoertzen/).
maintained by:
Mohamed Barakat (https://mohamed-barakat.github.io) and
Sebastian Gutsche (https://sebasguts.github.io).
Homepage: https://homalg-project.github.io/pkg/Gauss
Report issues at https://github.com/homalg-project/homalg_project/issues
─────────────────────────────────────────────────────────────────────────────
true
gap> SN := SparseMatrix( 2, 3, [ [ 2 ], [ 1, 3 ] ], [ [ 1 ], [ 3, 2 ] ] * One( GF(3) ) );
<a 2 x 3 sparse matrix over GF(3)>
gap> Rank(SN);
Error, no method found! For debugging hints type ?Recovery from NoMethodFound
Error, no 2nd choice method found for `RankDestructive' on 2 arguments at $(GAPPATH)/lib/
methsel2.g:250 called from
RankDestructive( CopyMat( mat ), mat!.ncols
) at $(GAPPATH)/pkg/gauss/gap/Sparse.gi:396 called from
<function "Rank method for sparse matrices">( <arguments> )
called from read-eval loop at *stdin*:3
type 'quit;' to quit to outer loop
brk>
It would be nice if gauss could handle this more gracefully. Moreover, if zero entries are not permitted, then I would recommend stating this more clearly in the documentation. (In my opinion, it would be better if gauss automatically processed such entries so that it doesn't have any problems with it later on.)