#10902: proof=False unnecessary in factor()
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Reporter: zimmerma | Owner: malb
Type: defect | Status:
needs_review
Priority: critical | Milestone: sage-5.0
Component: commutative algebra | Resolution:
Keywords: sd34 | Work issues:
Report Upstream: N/A | Reviewers:
Authors: Martin Albrecht, Paul Zimmermann | Merged in:
Dependencies: #10903 | Stopgaps:
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Changes (by malb):
* status: needs_work => needs_review
* work_issues: Proof=... still present =>
Old description:
> {{{
> sage: R.<x,y> = GF(2)[]
> sage: p = x^3*y^7 + x^2*y^6 + x^2*y^3
> sage: q = x^3*y^5
> sage: f = p*q
> sage: p.factor(proof=False)*q.factor(proof=False)
> x^5 * y^8 * (x*y^4 + y^3 + 1)
> sage: f.factor(proof=False)
> x^5 * y^6 * (x*y^4 + y^3 + 1)
> sage: f
> x^6*y^12 + x^5*y^11 + x^5*y^8
> }}}
> It seems a factor {{{y^2}}} has been lost in the factorization of
> {{{f}}} (in addition to the fact that the factorization of {{{f}}}
> might be incomplete).
>
> I mark this as critical since we should have at least the following
> equality:
> {{{
> sage: f.factor(proof=False).expand() == f
> False
> }}}
New description:
There are currently no known counter examples where Singular would return
an incorrect factorisation. It might be very very slow but does not return
wrong answers as far as we know. Hence, we should drop {{{proof=False}}}.
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/10902#comment:21>
Sage <http://www.sagemath.org>
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