#10763: Speedup of matrix multiplication
------------------------------+---------------------------------------------
Reporter: SimonKing | Owner: jason, was
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-4.6.2
Component: linear algebra | Keywords: matrix multiplication
Author: Simon King | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
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Changes (by SimonKing):
* status: needs_work => needs_review
Comment:
The test failures were caused by a very stupid mistake:
`self.new_matrix()` by default assumes that the dimension of the new
matrix is the same as the dimension of the old matrix. In the
multiplication algorithms, I saw
`self.new_matrix(nrows=self.nrows(),...)`, was not reading further, and
thought that we are in the default case, thus, deleted the arguments.
Of course, it continues "(..., ncols=right.ncols())`.
What I did now was to avoid calling `self.nrows()` and `right.ncols()` -
direct access to the attributes `self._nrows` and `right._ncols` is
faster.
To my surprise, the timings improved a little more:
{{{
sage: def test(M):
....: for i in xrange(10^6):
....: M*=M
....: return M
....:
sage: m = matrix(GF(3),[[1]])
sage: %time test(m)
CPU times: user 36.67 s, sys: 0.16 s, total: 36.83 s
Wall time: 36.95 s
[1]
sage: m = matrix(GF(2),[[1]])
sage: %time test(m)
CPU times: user 26.29 s, sys: 0.14 s, total: 26.43 s
Wall time: 26.50 s
[1]
}}}
Is it faster to provide arguments with a default value ''explicitly''?
The tests for `sage/matrix/` passed. I am now running all doctests (not
the long ones), but I think I can already revert it to "needs review".
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/10763#comment:8>
Sage <http://www.sagemath.org>
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