Closed
Description
Describe the bug
Unexpected GAP error, see below
To Reproduce
All smaller examples that I tried didn't run into this issue.
This was run on the branch of #4753, as otherwise one encounters #4752 before this issue.
julia> cube = permutation_group(48, [gen_up, gen_left, gen_front, gen_right, gen_back, gen_down])
Permutation group of degree 48
julia> gen_up = @perm 48 ( 1, 3, 8, 6)( 2, 5, 7, 4)( 9,33,25,17)(10,34,26,18)(11,35,27,19);
julia> gen_left = @perm 48 ( 9,11,16,14)(10,13,15,12)( 1,17,41,40)( 4,20,44,37)( 6,22,46,35);
julia> gen_front = @perm 48 (17,19,24,22)(18,21,23,20)( 6,25,43,16)( 7,28,42,13)( 8,30,41,11);
julia> gen_right = @perm 48 (25,27,32,30)(26,29,31,28)( 3,38,43,19)( 5,36,45,21)( 8,33,48,24);
julia> gen_back = @perm 48 (33,35,40,38)(34,37,39,36)( 3, 9,46,32)( 2,12,47,29)( 1,14,48,27);
julia> gen_down = @perm 48 (41,43,48,46)(42,45,47,44)(14,22,30,38)(15,23,31,39)(16,24,32,40);
julia> cube = permutation_group(48, [gen_up, gen_left, gen_front, gen_right, gen_back, gen_down])
Permutation group of degree 48
julia> orbs = orbits(cube)
2-element Vector{Oscar.GSetByElements{PermGroup, Int64}}:
G-set of cube with seeds [1, 3, 17, 14, 8, 38, 9, 41, 19, 48, 22, 6, 30, 33, 43, 11, 46, 40, 24, 27, 25, 35, 16, 32]
G-set of cube with seeds [2, 5, 12, 7, 36, 10, 47, 4, 28, 45, 34, 13, 29, 44, 20, 42, 26, 21, 37, 15, 31, 18, 23, 39]
julia> bl = blocks(orbs[1])
G-set of
permutation group of degree 48
with seeds [[1, 9, 35], [3, 33, 27], [17, 6, 11], [14, 46, 40], [8, 19, 25], [38, 48, 32], [41, 22, 16], [30, 43, 24]]
julia> h = action_homomorphism(bl)
Group homomorphism
from permutation group of degree 48
to Sym(8)
julia> image(h)
ERROR: Error thrown by GAP: Error, no method found! For debugging hints type ?Recovery from NoMethodFound
Error, no 1st choice method found for `LargestMovedPoint' on 1 arguments at /home/lgoe/.julia/artifacts/8db0b2a1c30ae8f18d09d8f93b7cb5b1b359722d/share/gap/lib/methsel2.g:250 called from
<function "HANDLE_METHOD_NOT_FOUND">( <arguments> )
called from read-eval loop at *defin*:0
Stacktrace:
[1] error(s::String)
@ Base ./error.jl:35
[2] ThrowObserver(depth::Int32)
@ GAP ~/.julia/packages/GAP/bMh5a/src/GAP.jl:101
[3] _call_gap_func
@ ~/.julia/packages/GAP/bMh5a/src/ccalls.jl:343 [inlined]
[4] (::GapObj)(a1::GapObj)
@ GAP ~/.julia/packages/GAP/bMh5a/src/ccalls.jl:320
[5] LargestMovedPoint(x::GapObj)
@ Oscar.GAPWrap ~/code/julia/Oscar.jl/src/GAP/wrappers.jl:282
[6] _oscar_subgroup(obj::GapObj, G::PermGroup)
@ Oscar ~/code/julia/Oscar.jl/src/Groups/types.jl:456
[7] _as_subgroup_bare
@ ~/code/julia/Oscar.jl/src/Groups/sub.jl:8 [inlined]
[8] _as_subgroup
@ ~/code/julia/Oscar.jl/src/Groups/sub.jl:12 [inlined]
[9] image(f::GAPGroupHomomorphism{PermGroup, PermGroup})
@ Oscar ~/code/julia/Oscar.jl/src/Groups/homomorphisms.jl:345
[10] top-level scope
@ REPL[192]:1
Expected behavior
Return me a subgroup of Sym(8), as one would expect when calling image on a group hom with that codomain.
System (please complete the following information):
julia> Oscar.versioninfo(full=true)
OSCAR version 1.4.0-DEV - #lg/orbit-caching, 3076dc6532 -- 2025-03-21 15:38:07 +0100
combining:
AbstractAlgebra.jl v0.44.10
GAP.jl v0.13.1
Hecke.jl v0.35.15
Nemo.jl v0.49.3
Polymake.jl v0.11.28
Singular.jl v0.25.2
building on:
FLINT_jll v300.200.100+0
GAP_jll v400.1400.3+0
GAP_lib_jll v400.1400.4+0
Singular_jll v404.100.104+0
libpolymake_julia_jll v0.13.2+0
libsingular_julia_jll v0.47.2+0
polymake_jll v400.1300.3+0
polymake_oscarnumber_jll v0.3.5+0
See `]st -m` for a full list of dependencies.
Julia Version 1.11.4
Commit 8561cc3d68d (2025-03-10 11:36 UTC)
Build Info:
Official https://julialang.org/ release
Additional context
This is now indeed due to @mjrodgers recent changes to the G-Sets (as the setup didn't even work before that). I have no idea if it is an issue with the new code, or deep inside of GAP, or dunno.