Merge pull request #1324 from sumiya11/groebner-ord

In Groebner extension, partially fix ordering

Project.toml

@@ -69,7 +69,7 @@ DocStringExtensions = "0.9"
 DomainSets = "0.6, 0.7"
 DynamicPolynomials = "0.5, 0.6"
 ForwardDiff = "0.10.36"
-Groebner = "0.5, 0.6, 0.7"
+Groebner = "0.8"
 IfElse = "0.1"
 LaTeXStrings = "1.3"
 LambertW = "1.0.0"

ext/SymbolicsGroebnerExt.jl

@@ -33,9 +33,16 @@ julia> @variables x y;
 julia> groebner_basis([x*y^2 + x, x^2*y + y])
 ```
 """
-function Symbolics.groebner_basis(polynomials::Vector{Num}; kwargs...)
+function Symbolics.groebner_basis(polynomials::Vector{Num}; ordering=InputOrdering(), kwargs...)
     polynoms, pvar2sym, sym2term = Symbolics.symbol_to_poly(polynomials)
-    basis = Groebner.groebner(polynoms; kwargs...)
+    sym2term_for_groebner = Dict{Any,Any}(v1 => k for (k, (v1, v2)) in sym2term)
+    all_sym_vars = Groebner.ordering_variables(ordering)
+    missed = setdiff(all_sym_vars, Set(collect(keys(sym2term_for_groebner))))
+    for var in missed
+        sym2term_for_groebner[var] = var
+    end
+    ordering = Groebner.ordering_transform(ordering, sym2term_for_groebner )
+    basis = Groebner.groebner(polynoms; ordering=ordering, kwargs...)
     PolyType = symtype(first(polynomials))
     Symbolics.poly_to_symbol(basis, pvar2sym, sym2term, PolyType)
 end

test/extensions/groebner.jl

@@ -72,5 +72,13 @@ truebasis = [
 basis = groebner_basis(system)
 @test isequal(expand.(basis), truebasis)
 
+# issues/1323
+@variables t S(t) R(t)
+sys = [-12 + 5S, 2 + 5R]
+@test isequal(expand.(groebner_basis(sys, ordering=Lex(S, R))), [2//5 + R, -12//5 + S])
+sys = [S^2 + 2*R^2 - 1, S*R - 1]
+res = [(1//2) - (1//2)*(R^2) + R^4, S - R + (2//1)*(R^3)]
+@test isequal(expand.(groebner_basis(sys, ordering=Lex(S, R))), res)
+
 # Groebner does not yet work with constant ideals
 @test_broken groebner_basis([1])