#4260: use LinBox as native matrix representation for dense matrices over GF(p)
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Reporter: malb | Owner: cpernet
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-4.7.2
Component: linear algebra | Keywords: linbox, linear algebra,
sd32
Work_issues: improve echelonize | Upstream: N/A
Reviewer: | Author: Burcin Erocal, Martin
Albrecht, Rob Beezer
Merged: | Dependencies:
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Comment(by cpernet):
A word about the regression (I'm copying my reply to malb on linbox-devel)
The new code (that I wrote )
{{{
size_t r = FFPACK::ReducedRowEchelonForm(F, nrows, ncols, matrix, ncols,
P,Q);
}}}
calls the actual RowEchelon elimination in FFPACK, which transforms A into
its redrowechelon form E and the transformation matrix U (both matrices
being magically stored inplace in A)
It is slower than the older code sage-4.6 using linbox-1.1.6:
{{{
int rank = EF.rowReducedEchelon(E, A);
}}}
The latter computes the redrowechlon (actually the trans of the
redcolechelon), but no transformation matrix.
This saves roughly 50% of the total number of arithmetic ops (1n^3 rather
than 2n^3), and explains the regression.
Switching back to the old way should fix the regression (for a quick fix).
And I still need to add the feature of not computing the transform at the
level of FFPACK, since I expect some timing improvements over the old
version in linbox 1.1.6.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/4260#comment:21>
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