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divrem with flag complete_reduction #681

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merged 3 commits into from
Jul 28, 2023
Merged

divrem with flag complete_reduction #681

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eb2c794
divrem with flag complete_reduction
hannes14 Jul 24, 2023
79673e8
complete_reduction for reduce (#682)
hannes14 Jul 25, 2023
58f4e7b
implementation via idLift and options
hannes14 Jul 28, 2023
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32 changes: 22 additions & 10 deletions src/ideal/ideal.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -689,10 +689,14 @@ left reduction, and hence cannot be used to test containment in a two-sided idea
For LETTERPLACE rings (S <: slpalg, FreeAlgebra), the reduction is two-sided as
only two-sided ideals can be constructed here.
"""
function reduce(I::sideal{S}, G::sideal{S}) where S <: SPolyUnion
function reduce(I::sideal{S}, G::sideal{S};complete_reduction::Bool = true) where S <: SPolyUnion
check_parent(I, G)
R = base_ring(I)
ptr = GC.@preserve I G R libSingular.p_Reduce(I.ptr, G.ptr, R.ptr)
if complete_reduction
ptr = GC.@preserve I G R libSingular.p_Reduce(I.ptr, G.ptr, R.ptr)
else
ptr = GC.@preserve I G R libSingular.p_Reduce(I.ptr, G.ptr, R.ptr,1)
end
return sideal{S}(R, ptr, false, I.isTwoSided)
end

Expand All @@ -706,10 +710,14 @@ left reduction, and hence cannot be used to test membership in a two-sided ideal
For LETTERPLACE rings (S <: slpalg, FreeAlgebra), the reduction is the full
two-sided reduction as only two-sided ideals can be constructed here.
"""
function reduce(p::S, G::sideal{S}) where S <: SPolyUnion
function reduce(p::S, G::sideal{S};complete_reduction = true) where S <: SPolyUnion
R = parent(p)
R == base_ring(G) || error("Incompatible base rings")
ptr = GC.@preserve p G R libSingular.p_Reduce(p.ptr, G.ptr, R.ptr)
if complete_reduction
ptr = GC.@preserve p G R libSingular.p_Reduce(p.ptr, G.ptr, R.ptr)
else
ptr = GC.@preserve p G R libSingular.p_Reduce(p.ptr, G.ptr, R.ptr,1)
end
return R(ptr)
end

Expand Down Expand Up @@ -739,20 +747,24 @@ function division(I::sideal{S}, G::sideal{S}) where S <: SPolyUnion
end

@doc raw"""
divrem(I::sideal{S}, G::sideal{S}) where S <: SPolyUnion
divrem(I::sideal{S}, G::sideal{S}; complete_reduction::Bool = false) where S <: SPolyUnion

Computes a division with remainder of the generators of `I` by
the generators of `G`. Returns a tuple (Quo, Rem, U) where
`Matrix(I)*Matrix(U) = Matrix(G)*Matrix(Quo) + Matrix(Rem)`
`Matrix(I)*U = Matrix(G)*Matrix(Quo) + Matrix(Rem)`
and `Rem = normalform(I, G)`. `U` is a diagonal matrix of units differing
from the identity matrix only for local ring orderings.
"""
function divrem(I::sideal{S}, G::sideal{S}) where S <: SPolyUnion
function divrem(I::sideal{S}, G::sideal{S}; complete_reduction::Bool = false) where S <: SPolyUnion
check_parent(I, G)
R = base_ring(I)
ptr_T,ptr_Rest,ptr_U = GC.@preserve I G R libSingular.id_DivRem_Unit(I.ptr, G.ptr,
R.ptr)
return (smodule{S}(R,ptr_T), sideal{S}(R,ptr_Rest), smodule{S}(R,ptr_U))
old_redsb=libSingular.set_option("OPT_REDSB",complete_reduction)
old_redtail=libSingular.set_option("OPT_REDTAIL",complete_reduction)
ptr_T,ptr_Rest,ptr_U = GC.@preserve I G R libSingular.id_Lift(G.ptr, I.ptr, true,
false, true, R.ptr)
libSingular.set_option("OPT_REDSB",old_redsb)
libSingular.set_option("OPT_REDTAIL",old_redtail)
return (smodule{S}(R,ptr_T), sideal{S}(R,ptr_Rest), smatrix{S}(R,ptr_U))
end

###############################################################################
Expand Down
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