#18231: constructing matrices is very slow
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Reporter: vdelecroix | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-6.7
Component: linear algebra | Keywords:
Merged in: | Authors:
Reviewers: | Report Upstream: N/A
Work issues: | Branch:
Commit: | Dependencies:
Stopgaps: |
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The problem is in the code which looks like the following
{{{
def test1():
K = QuadraticField(2)
for _ in range(100):
i = randint(2,3)
j = randint(2,3)
m = matrix(K, i, j, range(i*j))
}}}
It causes the various matrix spaces to rebuilt almost each time! If we
compare with
{{{
def test2():
K = QuadraticField(2)
M = {(i,j): MatrixSpace(K,i,j) for i in range(2,4) for j in
range(2,4)}
for _ in range(100):
i = randint(2,3)
j = randint(2,3)
m = M[i,j](range(i*j))
}}}
then we got
{{{
sage: %timeit test1()
10 loops, best of 3: 55 ms per loop
sage: %timeit test2()
100 loops, best of 3: 6.49 ms per loop
}}}
This is one of the reason why the creation of Polyhedron is so slow (see
#18213).
--
Ticket URL: <http://trac.sagemath.org/ticket/18231>
Sage <http://www.sagemath.org>
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