#18231: constructing matrices is very slow
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Reporter: vdelecroix | Owner:
Type: defect | Status: needs_review
Priority: major | Milestone: sage-6.7
Component: linear algebra | Resolution:
Keywords: | Merged in:
Authors: Vincent Delecroix | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/vdelecroix/18231 | 715f49ecab8ae8bb66725be77da51ce6eb8f8738
Dependencies: | Stopgaps:
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Description changed by vdelecroix:
Old description:
> 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).
>
> In the branch we:
> - replace some old Cython code in `matrix_generic_dense` and `matrix0`
> and do some optimization
> - move the function `_get_matrix_class` in `MatrixSpace` out of the class
> (as it depends only on the base ring and the sparseness)
> - In the class `MatrixSpace` the argument `__matrix_class` is now
> `_matrix_class`. That way, it is possible in other part of Sage to
> optimize the creation of matrices by calling directly
> {{{
> sage: M = MatrixSpace(ZZ,3,2)
> sage: M._matrix_class([1,5,3,-1,2,3], coerce=False, copy=False)
> }}}
> - we simplify the main element constructor of matrix, namely
> `MatrixSpace.matrix` and gain a significant speedup.
New description:
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).
In the branch we:
- replace some old Cython code in `matrix_generic_dense` and `matrix0` and
do some optimization
- move the function `_get_matrix_class` in `MatrixSpace` out of the class
(as it depends only on the base ring and the sparseness)
- In the class `MatrixSpace` the argument `__matrix_class` is now
`_matrix_class`. That way, it is possible in other part of Sage to
optimize the creation of matrices by calling directly
{{{
sage: M = MatrixSpace(ZZ,3,2)
sage: M._matrix_class([1,5,3,-1,2,3], coerce=False, copy=False)
}}}
- we simplify the main element constructor of matrix, namely
`MatrixSpace.matrix` and gain a significant speedup.
follow up: #18258
--
--
Ticket URL: <http://trac.sagemath.org/ticket/18231#comment:9>
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