#3436: random_matrix() with prescribed density buggy
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Reporter: rpw | Owner: was
Type: defect | Status: needs_review
Priority: major | Milestone: sage-4.3.1
Component: linear algebra | Keywords:
Work_issues: | Author: spancratz
Upstream: N/A | Reviewer:
Merged: |
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Changes (by newvalueoldvalue):
* status: new => needs_review
* upstream: => N/A
* author: => spancratz
Comment:
Attached a patch. It introduces a new method in ``ring.pyx``,
``_random_nonzero_element``, which by default calls ``random_element``
until a non-zero element has been obtained.
On the matrix end, I've introduced a new parameter ``nonzero`` to the
``randomize`` methods in the various matrix implementations. If this is
set to ``True``, the modified entries are guaranteed to be non-zero,
whereas if it is set to ``False`` they are not. The method
``random_element`` on a matrix space now calls ``randomize`` on a zero
matrix with ``nonzero=True``.
Finally, this is now also used to ensure that generating a fraction field
element does not cause a division by zero error.
Sebastian
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/3436#comment:5>
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