#18598 closed defect (worksforme)
reduce method of polynomial ideals gives incorrect results
Reported by: | lftabera | Owned by: | |
---|---|---|---|
Priority: | major | Milestone: | sage-duplicate/invalid/wontfix |
Component: | algebra | Keywords: | days94 |
Cc: | dimpase | Merged in: | |
Authors: | Reviewers: | Dima Pasechnik | |
Report Upstream: | N/A | Work issues: | |
Branch: | Commit: | ||
Dependencies: | Stopgaps: |
Description (last modified by )
Define the following polynomial ring, polynomial, and ideal:
sage: term_order = TermOrder('degrevlex', 2) + TermOrder('degrevlex', 2) sage: K = PolynomialRing(QQ, 'x,y,a0,a1', order=term_order) sage: x, y, a0, a1 = K.gens() sage: f = x**3 + x**2*y sage: m = Ideal(x**4, x**2*y, y**2)
Before #27508, we get an incorrect reduction:
sage: m.reduce(f) == f.reduce(m.groebner_basis()) False sage: m.reduce(f) x^3 + x^2*y sage: f.reduce(m.groebner_basis()) x^3
Singular computes correctly the reduction as x^3
.
The problem is we call singular via libsingular without asking for tail reduction.
This was fixed in #27508, after which we get correct results:
sage: m.reduce(f) == f.reduce(m.groebner_basis()) True sage: m.reduce(f) x^3 sage: f.reduce(m.groebner_basis()) x^3
Change History (7)
comment:1 Changed 3 years ago by
- Keywords days94 added
- Milestone changed from sage-6.8 to sage-8.3
comment:2 Changed 3 years ago by
comment:3 Changed 3 years ago by
- Milestone changed from sage-8.3 to sage-8.4
update milestone 8.3 -> 8.4
comment:4 Changed 8 months ago by
- Cc dimpase added
- Milestone changed from sage-8.4 to sage-duplicate/invalid/wontfix
- Status changed from new to needs_review
This works correctly in 9.2.beta10, possibly since #27508.
comment:5 Changed 8 months ago by
- Reviewers set to Dima Pasechnik
- Status changed from needs_review to positive_review
indeed
comment:6 Changed 6 months ago by
- Resolution set to worksforme
- Status changed from positive_review to closed
comment:7 Changed 6 months ago by
- Description modified (diff)
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I am not able to debug this. For me, it seems that this is an error in libsingular and, probably, a duplicate of #12529