residue_ring of a residue_ring is very slow

[JohnAAbbott]

Describe the bug
The last command below takes a long time -- I did not wait for it to finish. It can also be reproduced using only AbstractAlgebra

To Reproduce
Steps to reproduce the behaviour, please provide a code snippet that triggers
the bug.

# using Pkg; Pkg.develop(path="/home/zez25zuh/OSCAR/GIT/AbstractAlgebra.jl");
# using AbstractAlgebra
P,(x,y) = polynomial_ring(QQ, ["x", "y"]);
f = x+y+1;
R,phi = residue_ring(P,f);
residue_ring(R, phi(x))

Expected behavior
A bit faster?

System (please complete the following information):
Please paste the output of Oscar.versioninfo(full=true) below. If this does
not work, please paste the output of Julia's versioninfo() and your Oscar
version.

julia> Oscar.versioninfo(full=true)
OSCAR version 1.3.0-DEV - #master, 409d74e527 -- 2024-12-17 11:22:07 +0100
  combining:
    AbstractAlgebra.jl   v0.44.1 - #master, c10f88063e -- 2024-12-19 18:04:37 +0100
    GAP.jl               v0.12.2
    Hecke.jl             v0.35.0
    Nemo.jl              v0.48.0 - #JAA/is_nilpotent, 0773b2670a -- 2024-12-18 14:46:53 +0100
    Polymake.jl          v0.11.23
    Singular.jl          v0.24.1
  building on:
    FLINT_jll               v300.100.300+0
    GAP_jll                 v400.1300.102+2
    Singular_jll            v404.1.700+0
    libpolymake_julia_jll   v0.13.0+0
    libsingular_julia_jll   v0.46.1+0
    polymake_jll            v400.1300.2+0
See `]st -m` for a full list of dependencies.

Julia Version 1.10.5
Commit 6f3fdf7b362 (2024-08-27 14:19 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: Linux (x86_64-linux-gnu)
  CPU: 20 × Intel(R) Core(TM) i9-10900 CPU @ 2.80GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-15.0.7 (ORCJIT, skylake)
Threads: 1 default, 0 interactive, 1 GC (on 20 virtual cores)
Environment:
  JULIA_LOAD_PATH = @:@v#.#:@stdlib:/environments/globalenv
  JULIA_DEPOT_PATH = /home/zez25zuh/.julia:
Official https://julialang.org/ release

Additional context
Add any other context about the problem here.

[joschmitt]

From what I can tell, the issue starts with using residue_ring on a multivariate polynomial ring. The method returns a EuclideanRingResidueRing, but the ring wasn't euclidean to start with. (I don't know what exact properties of the ring are required in the implementation.)
Maybe residue_ring should redirect to quo(::Ring, ::Ideal) in this case?

[fieker]

On Fri, Dec 20, 2024 at 01:59:22AM -0800, JohnAAbbott wrote: **Describe the bug** The last command below takes a long time -- I did not wait for it to finish. It can also be reproduced using only `AbstractAlgebra` **To Reproduce** Steps to reproduce the behaviour, please provide a code snippet that triggers the bug. ``` # using Pkg; Pkg.develop(path="/home/zez25zuh/OSCAR/GIT/AbstractAlgebra.jl"); # using AbstractAlgebra P,(x,y) = polynomial_ring(QQ, ["x", "y"]); f = x+y+1; R,phi = residue_ring(P,f); residue_ring(R, phi(x)) ``` **Expected behavior** A bit faster?

kind of user error... Q[x,y] is not euclidean but you (well the system) is calling a function for euclidean rings.... it dies trying to invert elements using euclids algorithm

…

**System (please complete the following information):** Please paste the output of `Oscar.versioninfo(full=true)` below. If this does not work, please paste the output of Julia's `versioninfo()` and your Oscar version. ``` julia> Oscar.versioninfo(full=true) OSCAR version 1.3.0-DEV - #master, 409d74e -- 2024-12-17 11:22:07 +0100 combining: AbstractAlgebra.jl v0.44.1 - #master, c10f88063e -- 2024-12-19 18:04:37 +0100 GAP.jl v0.12.2 Hecke.jl v0.35.0 Nemo.jl v0.48.0 - #JAA/is_nilpotent, 0773b2670a -- 2024-12-18 14:46:53 +0100 Polymake.jl v0.11.23 Singular.jl v0.24.1 building on: FLINT_jll v300.100.300+0 GAP_jll v400.1300.102+2 Singular_jll v404.1.700+0 libpolymake_julia_jll v0.13.0+0 libsingular_julia_jll v0.46.1+0 polymake_jll v400.1300.2+0 See `]st -m` for a full list of dependencies. Julia Version 1.10.5 Commit 6f3fdf7b362 (2024-08-27 14:19 UTC) Build Info: Official https://julialang.org/ release Platform Info: OS: Linux (x86_64-linux-gnu) CPU: 20 × Intel(R) Core(TM) i9-10900 CPU @ 2.80GHz WORD_SIZE: 64 LIBM: libopenlibm LLVM: libLLVM-15.0.7 (ORCJIT, skylake) Threads: 1 default, 0 interactive, 1 GC (on 20 virtual cores) Environment: JULIA_LOAD_PATH = @***@***.******@***.***:/environments/globalenv JULIA_DEPOT_PATH = /home/zez25zuh/.julia: Official https://julialang.org/ release ``` **Additional context** Add any other context about the problem here. -- Reply to this email directly or view it on GitHub: #4410 You are receiving this because you are subscribed to this thread. Message ID: ***@***.***>

[fieker]

On Fri, Dec 20, 2024 at 01:59:22AM -0800, JohnAAbbott wrote: **Describe the bug** The last command below takes a long time -- I did not wait for it to finish. It can also be reproduced using only `AbstractAlgebra` **To Reproduce** Steps to reproduce the behaviour, please provide a code snippet that triggers the bug. ``` # using Pkg; Pkg.develop(path="/home/zez25zuh/OSCAR/GIT/AbstractAlgebra.jl"); # using AbstractAlgebra P,(x,y) = polynomial_ring(QQ, ["x", "y"]); f = x+y+1; R,phi = residue_ring(P,f); residue_ring(R, phi(x)) ``` **Expected behavior** A bit faster?

julia> quo(P, [f]) (Quotient of multivariate polynomial ring by ideal (x + y + 1), Map: P -> quotient of multivariate polynomial ring)

…

**System (please complete the following information):** Please paste the output of `Oscar.versioninfo(full=true)` below. If this does not work, please paste the output of Julia's `versioninfo()` and your Oscar version. ``` julia> Oscar.versioninfo(full=true) OSCAR version 1.3.0-DEV - #master, 409d74e -- 2024-12-17 11:22:07 +0100 combining: AbstractAlgebra.jl v0.44.1 - #master, c10f88063e -- 2024-12-19 18:04:37 +0100 GAP.jl v0.12.2 Hecke.jl v0.35.0 Nemo.jl v0.48.0 - #JAA/is_nilpotent, 0773b2670a -- 2024-12-18 14:46:53 +0100 Polymake.jl v0.11.23 Singular.jl v0.24.1 building on: FLINT_jll v300.100.300+0 GAP_jll v400.1300.102+2 Singular_jll v404.1.700+0 libpolymake_julia_jll v0.13.0+0 libsingular_julia_jll v0.46.1+0 polymake_jll v400.1300.2+0 See `]st -m` for a full list of dependencies. Julia Version 1.10.5 Commit 6f3fdf7b362 (2024-08-27 14:19 UTC) Build Info: Official https://julialang.org/ release Platform Info: OS: Linux (x86_64-linux-gnu) CPU: 20 × Intel(R) Core(TM) i9-10900 CPU @ 2.80GHz WORD_SIZE: 64 LIBM: libopenlibm LLVM: libLLVM-15.0.7 (ORCJIT, skylake) Threads: 1 default, 0 interactive, 1 GC (on 20 virtual cores) Environment: JULIA_LOAD_PATH = @***@***.******@***.***:/environments/globalenv JULIA_DEPOT_PATH = /home/zez25zuh/.julia: Official https://julialang.org/ release ``` **Additional context** Add any other context about the problem here. -- Reply to this email directly or view it on GitHub: #4410 You are receiving this because you are subscribed to this thread. Message ID: ***@***.***>

[joschmitt]

Funnily enough, if I do

R, phi = quo(R, f);
quo(R, phi(x));

I still get a EuclideanRingResidueRing in the end.

P.S.: quo(R, ideal(phi(x))) works correctly.

[JohnAAbbott]

The original context was trying to create a test case in AbstractAlgebra to achieve better code coverage; I think it is not worth investing more time in trying to construct such an input.
In any case, it is not good that residue_ring returns a EuclideanRingResidueRing when the result clearly is not -- it should either produce an error or give a correct result. I did not see anything in the documentation about restrictions on arguments for residue_ring.

[joschmitt]

I created #4412 for the problems with residue_ring vs. quo.

I close this issue in favour of #4412.