Another bug in ideals triggered by trying to find maximal subsemigroups

Issue #107 resolved
James Mitchell
repo owner created an issue
gap> S:=[SymmetricInverseMonoid(2)];
[ <symmetric inverse semigroup on 2 pts> ]
gap> S[2]:=MaximalSubsemigroups(S[1]);
[ <partial perm monoid on 2 pts with 3 generators>, <partial perm semigroup 
   on 2 pts with 2 generators> ]
gap> S[3]:=List(S[2], MaximalSubsemigroups);
Error, no method found! For debugging hints type ?Recovery from NoMethodFound
Error, no 1st choice method found for `RhoOrb' on 1 arguments called from
RhoOrb( d ) called from
RClassReps( d[i] ) called from
PartialOrderOfDClasses( I ) called from
GeneratorsOfSemigroup( SemigroupIdeal( S, reps ) ) called from
func( C[i] ) called from
...  at line 3 of *stdin*
you can 'quit;' to quit to outer loop, or
you can 'return;' to continue
brk> 

The problem seems to be that the D-classes of I don't know that they belong to `IsInverseOpClass' and so the wrong method is used to find the RClassReps.

Comments (8)

  1. wilfwilson

    I have encountered a similar (identical) bug too:

    gap> gens := [ PartialPerm( [ 1, 2, 3, 4 ], [ 3, 2, 5, 4 ] ), 
    >  PartialPerm( [ 1, 2, 4 ], [ 3, 5, 4 ] ), 
    >  PartialPerm( [ 1, 2, 3, 4 ], [ 5, 2, 3, 1 ] ), 
    >  PartialPerm( [ 1, 3, 4, 5 ], [ 5, 3, 4, 1 ] ), 
    >  PartialPerm( [ 1, 2, 3, 4, 5 ], [ 5, 4, 3, 2, 1 ] ) ];;
    gap> S := InverseSemigroup(gens);
    <inverse partial perm semigroup on 5 pts with 5 generators>
    gap> S := Semigroup(S);
    <partial perm semigroup on 5 pts with 8 generators>
    gap> MaximalSubsemigroups(S);
    #I  finding an irredundant generating set...
    #I  element has larger rank than any element of semigroup.
    at  8 of    8 with  2 redundant,    5 non-redundant
    #I  find the D-class of each generator...
    #I  finding maximal subsemigroups arising from maximal D-classes...
    #I  considering D-class 3.
    #I  calculating the ideal S minus D...
    Error, no method found! For debugging hints type ?Recovery from NoMethodFound
    Error, no 1st choice method found for `RhoOrb' on 1 arguments called from
    RhoOrb( d 
     ) on line 1254 of file /Users/Wilf/Documents/GAP/pkg/semigroups/gap/greens.gi\
     called from
    RClassReps( d[i] 
     ) on line 1088 of file /Users/Wilf/Documents/GAP/pkg/semigroups/gap/inverse.g\
    i called from
    PartialOrderOfDClasses( I 
     ) on line 153 of file /Users/Wilf/Documents/GAP/pkg/semigroups/gap/ideals-act\
    ing.gi called from
    GeneratorsOfSemigroup( V 
     ) on line 663 of file /Users/Wilf/Documents/GAP/pkg/semigroups/gap/maximal.gi\
     called from
    <function "unknown">( <arguments> )
     called from read-eval loop at line 35 of *stdin*
    you can 'quit;' to quit to outer loop, or
    you can 'return;' to continue
    
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