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danielrademacher / BruhatDecomposition

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why does BruhatDecompositionSp fail for some matrices #4

Closed qodesign closed 2 years ago

qodesign commented 2 years ago

I've been using the package for some time and works well most of the time. However for some matrices it seems to fail. In the gap code running Tst(1) works; Tst(2) fails : slp[1]=fail; in both cases I check that the matrix is in Sp(2n,2):

LoadPackage("BruhatDecomposition","0"); SetInfoLevel(InfoBruhat,0);

Tst:=function(mode)local mat,n,stdgens,slp;

if(mode=1)then n:=5; mat:=[ [0,0,0,0,0,0,0,0,0,1], [0,0,0,0,0,0,0,0,1,0], [0,0,0,0,0,0,0,1,0,0], [0,0,0,0,0,0,1,0,0,0], [0,0,0,0,1,0,0,1,1,0], [0,0,0,0,0,1,1,1,1,1], [0,0,0,1,1,0,0,0,1,1], [0,0,1,0,1,1,1,1,1,0], [0,1,0,0,1,1,0,1,1,1], [1,0,0,0,1,0,1,1,0,0]]*Z(2); fi;

if(mode=2)then n:=4; mat:=[ [1,0,0,0,0,0,0,0], [0,1,0,0,0,0,0,0], [0,0,1,0,0,0,0,0], [1,1,1,1,0,0,0,0], [0,0,0,0,1,0,0,0], [0,0,0,0,1,1,0,0], [0,0,0,0,1,0,1,0], [0,0,0,0,1,0,0,1]]*Z(2); fi;

Print(" mat in Sp(2n,2)? : ",mat in Sp(2*n,2),"\n");

stdgens:=LGOStandardGensSpEvenChar(2*n,2); slp:=BruhatDecompositionSp(stdgens,mat);

return slp; end;

danielrademacher commented 2 years ago

Hi @qodesign !

Thanks a lot for the issue and for using this package. You are absolutely right, there were an error in the glueing process of the different MSLP. This should be fixed now.

If you encounter other errors or have improvement ideas, feel free to contact me.

Best wishes Daniel Rademacher

qodesign commented 2 years ago

On my side the examples that failed before now work. Thanks for fixing this so quickly.