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fix bug in MakeImagesInfoLinearGeneralMappingByImages
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@cdwensley @fingolfin
cdwensley authored and fingolfin committed May 12, 2021
1 parent 1dd9023 commit 681b9fb
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3 changes: 1 addition & 2 deletions lib/vspchom.gi
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Original file line number Diff line number Diff line change
Expand Up @@ -317,8 +317,7 @@ BindGlobal( "MakeImagesInfoLinearGeneralMappingByImages", function( map )
x -> LinearCombination( B, x ) ) );
map!.corelations := Immutable( ech.relations );
map!.imagesbasispreimage := Immutable( List( ech.coeffs,
x -> LinearCombination( x,
mapi[2] ) ) );
x -> LinearCombination( mapi[2], x ) ) );

fi;
end );
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47 changes: 47 additions & 0 deletions tst/testbugfix/2021-05-11-LeftModHom.tst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,47 @@
#4481, issue reported by Chris Wensley
gap> G := Group( (1,2,3,4,5) );;
gap> F := GF(3);;
gap> A := GroupRing( F, G );;
gap> vecA := BasisVectors( Basis( A ) );;
gap> AI := AugmentationIdeal( A );;
gap> vecI := BasisVectors( Basis( AI ) );;
gap> maps := ListWithIdenticalEntries( 5, 0 );;
gap> for j in [1..5] do
> im := List( vecI, v -> v*vecA[j] );
> maps[j] := LeftModuleHomomorphismByImages( AI, AI, vecI, im );
> od;
gap> M := Algebra( F, maps );;
gap> hom := LeftModuleHomomorphismByImages( A, M, vecA, maps );
[ (Z(3)^0)*(), (Z(3)^0)*(1,2,3,4,5), (Z(3)^0)*(1,3,5,2,4),
(Z(3)^0)*(1,4,2,5,3), (Z(3)^0)*(1,5,4,3,2) ] ->
[ [ (Z(3)^0)*()+(Z(3))*(1,2,3,4,5), (Z(3)^0)*(1,2,3,4,5)+(Z(3))*(1,3,5,2,4),
(Z(3)^0)*(1,3,5,2,4)+(Z(3))*(1,4,2,5,3),
(Z(3)^0)*(1,4,2,5,3)+(Z(3))*(1,5,4,3,2) ] ->
[ (Z(3)^0)*()+(Z(3))*(1,2,3,4,5), (Z(3)^0)*(1,2,3,4,5)+(Z(3))*(1,3,5,2,4),
(Z(3)^0)*(1,3,5,2,4)+(Z(3))*(1,4,2,5,3),
(Z(3)^0)*(1,4,2,5,3)+(Z(3))*(1,5,4,3,2) ],
[ (Z(3)^0)*()+(Z(3))*(1,2,3,4,5), (Z(3)^0)*(1,2,3,4,5)+(Z(3))*(1,3,5,2,4),
(Z(3)^0)*(1,3,5,2,4)+(Z(3))*(1,4,2,5,3),
(Z(3)^0)*(1,4,2,5,3)+(Z(3))*(1,5,4,3,2) ] ->
[ (Z(3)^0)*(1,2,3,4,5)+(Z(3))*(1,3,5,2,4),
(Z(3)^0)*(1,3,5,2,4)+(Z(3))*(1,4,2,5,3),
(Z(3)^0)*(1,4,2,5,3)+(Z(3))*(1,5,4,3,2), (Z(3))*()+(Z(3)^0)*(1,5,4,3,2)
],
[ (Z(3)^0)*()+(Z(3))*(1,2,3,4,5), (Z(3)^0)*(1,2,3,4,5)+(Z(3))*(1,3,5,2,4),
(Z(3)^0)*(1,3,5,2,4)+(Z(3))*(1,4,2,5,3),
(Z(3)^0)*(1,4,2,5,3)+(Z(3))*(1,5,4,3,2) ] ->
[ (Z(3)^0)*(1,3,5,2,4)+(Z(3))*(1,4,2,5,3),
(Z(3)^0)*(1,4,2,5,3)+(Z(3))*(1,5,4,3,2), (Z(3))*()+(Z(3)^0)*(1,5,4,3,2),
(Z(3)^0)*()+(Z(3))*(1,2,3,4,5) ],
[ (Z(3)^0)*()+(Z(3))*(1,2,3,4,5), (Z(3)^0)*(1,2,3,4,5)+(Z(3))*(1,3,5,2,4),
(Z(3)^0)*(1,3,5,2,4)+(Z(3))*(1,4,2,5,3),
(Z(3)^0)*(1,4,2,5,3)+(Z(3))*(1,5,4,3,2) ] ->
[ (Z(3)^0)*(1,4,2,5,3)+(Z(3))*(1,5,4,3,2), (Z(3))*()+(Z(3)^0)*(1,5,4,3,2),
(Z(3)^0)*()+(Z(3))*(1,2,3,4,5), (Z(3)^0)*(1,2,3,4,5)+(Z(3))*(1,3,5,2,4)
],
[ (Z(3)^0)*()+(Z(3))*(1,2,3,4,5), (Z(3)^0)*(1,2,3,4,5)+(Z(3))*(1,3,5,2,4),
(Z(3)^0)*(1,3,5,2,4)+(Z(3))*(1,4,2,5,3),
(Z(3)^0)*(1,4,2,5,3)+(Z(3))*(1,5,4,3,2) ] ->
[ (Z(3))*()+(Z(3)^0)*(1,5,4,3,2), (Z(3)^0)*()+(Z(3))*(1,2,3,4,5),
(Z(3)^0)*(1,2,3,4,5)+(Z(3))*(1,3,5,2,4),
(Z(3)^0)*(1,3,5,2,4)+(Z(3))*(1,4,2,5,3) ] ]

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