#20490: Hash error with multivariate Laurent polynomial rings
-------------------------------------+-------------------------------------
Reporter: tscrim | Owner: tscrim
Type: defect | Status: needs_review
Priority: critical | Milestone: sage-7.2
Component: misc | Resolution:
Keywords: hash, | Merged in:
multivariate Laurent polynomials | Reviewers:
Authors: Travis Scrimshaw | Work issues:
Report Upstream: N/A | Commit:
Branch: | d52cd769c5c1dbe795914b5aa1a5f52367bafa7e
public/rings/hash_laurent_polynomial_ring-20490| Stopgaps:
Dependencies: |
-------------------------------------+-------------------------------------
Changes (by {'newvalue': u'Travis Scrimshaw', 'oldvalue': ''}):
* status: new => needs_review
* commit: => d52cd769c5c1dbe795914b5aa1a5f52367bafa7e
* branch: => public/rings/hash_laurent_polynomial_ring-20490
* author: => Travis Scrimshaw
Comment:
Thanks. That indeed did solve the problem.
With branch:
{{{
sage: R.<a,b> = LaurentPolynomialRing(ZZ)
sage: p = (a + b + ~b + 1)^10
sage: %timeit hash(p)
10000 loops, best of 3: 170 µs per loop
}}}
(without the cython changes is ~180 µs)
vs old version:
{{{
sage: p = (a + b + ~b + 1)^10
sage: %timeit hash(p)
10000 loops, best of 3: 34.2 µs per loop
}}}
Note that `p` has 121 terms with an upper degree of 10 and a lower degree
of -10. The fact that we only get ~6x slowdown here is acceptable to me.
(There's likely more speed to be gained from doing more cythonization of
the internal methods of the (Laurent) multivariate polynomials.)
----
New commits:
||[http://git.sagemath.org/sage.git/commit/?id=792d3a0dc1530178d12600cc02115937ae2dec56
792d3a0]||{{{Fixing the hash function of multivariate Laurent
polynomials.}}}||
||[http://git.sagemath.org/sage.git/commit/?id=d52cd769c5c1dbe795914b5aa1a5f52367bafa7e
d52cd76]||{{{Making some methods of multivariate polynomials cpdef.}}}||
--
Ticket URL: <http://trac.sagemath.org/ticket/20490#comment:2>
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