#11358: matrix multiplication over ZZ sometimes gives incorrect results
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Reporter: tomc | Owner:
Type: defect | Status: needs_work
Priority: critical | Milestone: sage-4.7.1
Component: linear algebra | Keywords: matrix multiplication,
multi-modular, integers, ZZ
Work_issues: | Upstream: N/A
Reviewer: | Author:
Merged: | Dependencies:
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Changes (by burcin):
* owner: jason, was =>
Comment:
Replying to [comment:11 tomc]:
> Also, in the new implementation of _new_random_prime() there is the
possibility of an infinite loop if self.moduli already contains all the
primes between self._lbound and self._ubound. I suggest modifying
_new_random_prime() so that it:
>
* makes some number of tries (10? 100?) to find a new random prime p in
the range self._lbound < p < self._ubound; and
>
* if this fails then it increases self_ubound and tries again.
I suggest raising an error instead of increasing `_ubound`. The upper
bound is usually set so that the primes fit in a single machine word. A
lot of things would break if this changed without notice.
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11358#comment:12>
Sage <http://www.sagemath.org>
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