Speed up polynomial mappings #4124
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| r = ngens(S) | ||
| ctx = MPolyBuildCtx(S) | ||
| for (c, e) in zip(AbstractAlgebra.coefficients(u), AbstractAlgebra.exponent_vectors(u)) | ||
| ee = [0 for _ in 1:r] |
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Suggested change
| ee = [0 for _ in 1:r] | |
| ee = Vector{Int}(undef, r) |
should be an epsilon faster
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One should be able to use the "same" vector ee for the whole loop as it gets copied anyway. I try to optimize this further.
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An undefined vector will not work. We need the zeroes.
HechtiDerLachs
commented
Sep 20, 2024
Comment on lines
+136
to
+137
| is_gen(x::MPolyQuoRingElem) = is_gen(lift(x)) | ||
| is_gen(x::MPolyDecRingElem) = is_gen(forget_grading(x)) |
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Memo to self: This is not legitimate. We need to switch to some internal method like _is_gen for that.
fingolfin
reviewed
Sep 20, 2024
| @@ -42,17 +42,37 @@ const _DomainTypes = Union{MPolyRing, MPolyQuoRing} | |||
| coeff_map::U | |||
| img_gens::Vector{V} | |||
| temp_ring # temporary ring used when evaluating maps | |||
| variable_indices::Vector{Int} # a table where the i-th entry contains the | |||
| # index of the variable where it's mapped to | |||
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| # index of the variable where it's mapped to | |
| # index of the variable where it is mapped to |
| @assert parent(g) === codomain "elements does not have the correct parent" | ||
| end | ||
| result = new{D, C, U, V}(domain, codomain, coeff_map, img_gens) | ||
| if all(is_gen(x) for x in img_gens) && allunique(img_gens) |
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| if all(is_gen(x) for x in img_gens) && allunique(img_gens) | |
| if all(is_gen, img_gens) && allunique(img_gens) |
| end | ||
| result = new{D, C, U, V}(domain, codomain, coeff_map, img_gens) | ||
| if all(is_gen(x) for x in img_gens) && allunique(img_gens) | ||
| result.variable_indices = [findfirst(x==y for y in gens(codomain)) for x in img_gens] |
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Suggested change
| result.variable_indices = [findfirst(x==y for y in gens(codomain)) for x in img_gens] | |
| result.variable_indices = [findfirst(==(x), gens(codomain)) for x in img_gens] |
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@fingolfin mentioned in his course this week that in the
RingFlattenings there was lots of potential improvements available via the use ofMPolyBuildCtx. I tried a little bit, but could not achieve any better performance. I'm wondering why, though, so I put it up here for discussion.