#10145: the charpoly method in matrix_integer_dense.pyx contains a note about it
being disabled on 64-bit computers, which is just not true
------------------------------+---------------------------------------------
Reporter: was | Owner: jason, was
Type: defect | Status: new
Priority: minor | Milestone: sage-4.6.1
Component: linear algebra | Keywords:
Author: | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
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Comment(by was):
ARGH. I just had the misfortune of actually *trying* to use Sage to
compute a bunch of charpolys on a 64-bit machine. Indeed, the comment
that the charpoly is disabled is wrong -- it's enabled. Unfortunately, it
*does* hang in many cases. More precisely, ever few hundred or so
charpoly's I tried to compute hung up completely (they should take seconds
and after 8 hours hadn't returned). Trying the same charpoly again did
work. This sucks.
What also sucks is that the Sage native charpoly is massively slower than
the linbox one (totally different algorithms):
{{{
sage: a = random_matrix(ZZ,100)
sage: time f = a.charpoly(algorithm='generic')
CPU times: user 6.49 s, sys: 0.01 s, total: 6.50 s
Wall time: 6.51 s
sage: a = random_matrix(ZZ,100)
sage: time f = a.charpoly(algorithm='linbox')
verbose 1 (<module>) computing charpoly of 100 x 100 matrix using linbox
verbose 1 (<module>) using linbox poly comp
verbose 1 (<module>) computed poly -- now converting back to Sage
verbose 1 (<module>) finished computing charpoly (time = 0.136902)
CPU times: user 0.14 s, sys: 0.00 s, total: 0.14 s
Wall time: 0.14 s
}}}
I'm really not sure what to do beside complain to Clement or rewrite
charpoly to maybe run two threads at once (?), or timeout and try again
after a certain amount of time (depending on the size of the input???).
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/10145#comment:1>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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