Flint integers bug?

[heiderich]

Is this a bug?

$ julia
               _
   _       _ _(_)_     |  A fresh approach to technical computing
  (_)     | (_) (_)    |  Documentation: https://docs.julialang.org
   _ _   _| |_  __ _   |  Type "?help" for help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 0.6.4 (2018-07-09 19:09 UTC)
 _/ |\__'_|_|_|\__'_|  |  Official http://julialang.org/ release
|__/                   |  x86_64-pc-linux-gnu

julia> using Cxx

julia> using Singular

Welcome to AbstractAlgebra version 0.0.9

AbstractAlgebra comes with absolutely no warranty whatsoever


Welcome to Nemo version 0.8.5

Nemo comes with absolutely no warranty whatsoever


julia> K = Nemo.ZZ
Integer Ring

julia> R,(x,y) = Singular.PolynomialRing(K, ["x","y"])
(Singular Polynomial Ring (Coeffs(18)),(x,y),(dp(2),C), Singular.spoly{Singular.n_unknown{Nemo.fmpz}}[x, y])

julia> I = [-x^4+2*x^2+y^4-y^2, -4*x^3*y-4*x*y^3+6*x*y]
2-element Array{Singular.spoly{Singular.n_unknown{Nemo.fmpz}},1}:
 -x^4+y^4+2*x^2-y^2    
 -4*x^3*y-4*x*y^3+6*x*y

julia> IAsIdeal = Ideal(R, I)
Singular Ideal over Singular Polynomial Ring (Coeffs(18)),(x,y),(dp(2),C) with generators (-x^4+y^4+2*x^2-y^2, -4*x^3*y-4*x*y^3+6*x*y)

julia> std(IAsIdeal)
ERROR: KeyError: key 0x00000000007fa7b0 not found
Stacktrace:
 [1] getindex at ./dict.jl:474 [inlined]
 [2] number_pop!(::Dict{UInt64,Singular.libSingular.live_cache}, ::Ptr{Void}) at /home/florian/.julia/v0.6/Singular/src/libsingular/coeffs.jl:230
 [3] fmpzExtGcd(::Cxx.CppPtr{Cxx.CxxQualType{Cxx.CppBaseType{:snumber},(false, false, false)},(false, false, false)}, ::Cxx.CppPtr{Cxx.CxxQualType{Cxx.CppBaseType{:snumber},(false, false, false)},(false, false, false)}, ::Ptr{Cxx.CppPtr{Cxx.CxxQualType{Cxx.CppBaseType{:snumber},(false, false, false)},(false, false, false)}}, ::Ptr{Cxx.CppPtr{Cxx.CxxQualType{Cxx.CppBaseType{:snumber},(false, false, false)},(false, false, false)}}, ::Cxx.CppPtr{Cxx.CxxQualType{Cxx.CppBaseType{:n_Procs_s},(false, false, false)},(false, false, false)}) at /home/florian/.julia/v0.6/Singular/src/libsingular/flint/fmpz.jl:175
 [4] #id_Std#2(::Bool, ::Function, ::Cxx.CppPtr{Cxx.CxxQualType{Cxx.CppBaseType{:sip_sideal},(false, false, false)},(false, false, false)}, ::Cxx.CppPtr{Cxx.CxxQualType{Cxx.CppBaseType{:ip_sring},(false, false, false)},(false, false, false)}) at /home/florian/.julia/v0.6/Singular/src/libsingular/ideals.jl:131
 [5] (::Singular.libSingular.#kw##id_Std)(::Array{Any,1}, ::Singular.libSingular.#id_Std, ::Cxx.CppPtr{Cxx.CxxQualType{Cxx.CppBaseType{:sip_sideal},(false, false, false)},(false, false, false)}, ::Cxx.CppPtr{Cxx.CxxQualType{Cxx.CppBaseType{:ip_sring},(false, false, false)},(false, false, false)}) at ./<missing>:0
 [6] #std#23(::Bool, ::Function, ::Singular.sideal{Singular.spoly{Singular.n_unknown{Nemo.fmpz}}}) at /home/florian/.julia/v0.6/Singular/src/ideal/ideal.jl:330
 [7] std(::Singular.sideal{Singular.spoly{Singular.n_unknown{Nemo.fmpz}}}) at /home/florian/.julia/v0.6/Singular/src/ideal/ideal.jl:329

[wbhart]

Yes, this looks like a bug. It looks like something got cleaned up that shouldn't have.

[hannes14]

Singular.n_unknown currently only supports fields - this maybe part of the problem

[wbhart]

It might be a bug in this code:

``` function fmpzExtGcd(a::number, b::number, s::Ptr{number}, t::Ptr{number}, cf::coeffs) n1 = julia(a)::Nemo.fmpz n2 = julia(b)::Nemo.fmpz s1 = unsafe_load(s) if s1 != C_NULL number_pop!(nemoNumberID, Ptr{Void}(s1)) end t1 = unsafe_load(t) if t1 != C_NULL number_pop!(nemoNumberID, Ptr{Void}(t1)) end g1, s1, t1 = gcdx(n1, n2) libSingular.setindex!(s, number(s1)) libSingular.setindex!(t, number(t1)) return number(g1) end ``` Andreas fixed a similar bug elsewhere. The code was not doing what Singular expects wrt s and t.

[rfourquet]

This seems to be fixed?

[wbhart]

I don't recall. Does it seem to give the right answer now? I do recall explaining how to fix it. And Andreas wrote something.

[rfourquet]

I didn't check if this gives the right answer, but at least it doesn't error:

julia> using Singular

julia> import Nemo

julia> K = Nemo.ZZ
Integer Ring

julia> R,(x,y) = Singular.PolynomialRing(K, ["x","y"])
(Singular Polynomial Ring (Coeffs(17)),(x,y),(dp(2),C), spoly{Singular.n_unknown{Nemo.fmpz}}[x, y])

julia> I = [-x^4+2*x^2+y^4-y^2, -4*x^3*y-4*x*y^3+6*x*y]
2-element Vector{spoly{Singular.n_unknown{Nemo.fmpz}}}:
 -x^4 + y^4 + 2*x^2 - y^2
 -4*x^3*y - 4*x*y^3 + 6*x*y

julia> IAsIdeal = Ideal(R, I)
Singular Ideal over Singular Polynomial Ring (Coeffs(17)),(x,y),(dp(2),C) with generators (-x^4+y^4+2*x^2-y^2, -4*x^3*y-4*x*y^3+6*x*y)

julia> std(IAsIdeal)
Singular Ideal over Singular Polynomial Ring (Coeffs(17)),(x,y),(dp(2),C) with generators (6*x*y, 2*x^3*y+2*x*y^3, x^4-y^4-2*x^2+y^2, 12*y^5-12*y^3, 2*x^2*y^3-4*y^5-2*x^2*y+4*y^3)

[wbhart]

Then we close the ticket.