#20470: Conversion of sparse to dense matrices over F2 is unspeakably slow
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Reporter: kedlaya | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-7.2
Component: linear algebra | Resolution:
Keywords: sparse matrices, dense | Merged in:
matrices | Reviewers:
Authors: | Work issues:
Report Upstream: N/A | Commit:
Branch: | Stopgaps:
Dependencies: |
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Comment (by jhpalmieri):
I think the culprit is the `matrix` method for the `MatrixSpace` class:
when you do `M2(...)`, it runs the `__call__` method, which does this:
{{{
return self.matrix(entries, coerce, copy)
}}}
Then the `matrix` method does this, if the input `x` is a matrix with the
right size:
{{{
x = x.list() # this is the slow part
...
x = list_to_dict(x, m, n)
}}}
So it should instead call `dense_matrix`.
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Ticket URL: <http://trac.sagemath.org/ticket/20470#comment:3>
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