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add prune_with_map_projection #751

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merged 5 commits into from
Jan 23, 2024
Merged

add prune_with_map_projection #751

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9c76b52
add prune_with_map_projection
hannes14 Jan 22, 2024
fb7a0cd
test prune_with_map_projection
hannes14 Jan 22, 2024
afb211e
Update src/module/module.jl
hannes14 Jan 22, 2024
8cc02b7
docstring for prune_with_map_projection
hannes14 Jan 22, 2024
ee96d75
Update src/module/module.jl
ederc Jan 22, 2024
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18 changes: 17 additions & 1 deletion src/module/module.jl
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Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
export jet, minimal_generating_set, ModuleClass, rank, smodule, slimgb,
eliminate, modulo, lift, division, divrem, prune_with_map
eliminate, modulo, lift, division, divrem, prune_with_map,
prune_with_map_projection

###############################################################################
#
Expand Down Expand Up @@ -407,6 +408,21 @@ function prune_with_map(I::smodule{spoly{T}}) where T <: Nemo.FieldElem
return smodule{spoly{T}}(R, r),smatrix{spoly{T}}(R,TT_ptr)
end

@doc raw"""
prune_with_map_projection(id::smodule{spoly{T}}) where T <: Nemo.FieldElem

Returns the module R minimally embedded in a free module such that the
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corresponding factor modules are isomorphic,
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I don't understand this docstring: There is one argument id; it is not stated how it related to R. And then the next line, is that transformation matrix meant to be another return value?

How about this (assuming I guessed the meaning right, which I probably didn't):

Suggested change
Returns the module R minimally embedded in a free module such that the
corresponding factor modules are isomorphic,
Return a module `R`, a transformation matrix `M` and a projection map `p`
satisfying the following properties: `R` is minimally embedded in a free
module `parent(R)` such that the quotient `parent(R)/R` is isomorphic to `id`,
with `M` describing this isomorphism, and `p` mapping `gen(id, i)` to
`gen(id, p(i))`

I am still rather confused by the usage of gen(i) (what is i? An index ranging over 1 .. ngens(id) maybe?!?), and why p[i] -- is p a vector, or a function, or what?

the transformation matrix of id to R and a projection p
which maps gen(i) to gen(p[i]).
"""
function prune_with_map_projection(I::smodule{spoly{T}}) where T <: Nemo.FieldElem
R = base_ring(I)
a = Vector{Int32}()
r, TT_ptr = GC.@preserve I R libSingular.id_prune_map_v(I.ptr, a, R.ptr)
return smodule{spoly{T}}(R, r),smatrix{spoly{T}}(R,TT_ptr),a
end

@doc raw"""
nres(id::smodule{spoly{T}}, max_length::Int) where T <: Nemo.FieldElem

Expand Down
5 changes: 5 additions & 0 deletions test/module/smodule-test.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -324,4 +324,9 @@ end
@test G[1] == vector(R, z)
@test T[3,1] == R(1)

G,T,p = prune_with_map_projection(M)
@test p[1] == 1
@test p[2] == 1
@test p[3] == 2

end
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