#5402: Sparse determinants are slow
----------------------------+-----------------------------------------------
Reporter: jbandlow | Owner: was
Type: enhancement | Status: new
Priority: major | Milestone: sage-3.4.2
Component: linear algebra | Keywords: determinant
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Comment(by jbandlow):
Sure, but as of right now, I've been waiting over fifteen minutes for
{{{
sage: dd = {(0,0):1}
sage: %time matrix(100,dd).det()
}}}
whereas
{{{
sage: %time matrix(100,dd,sparse=False).det()
CPU times: user 0.06 s, sys: 0.00 s, total: 0.06 s
Wall time: 0.08 s
}}}
So, currently, for a matrix large enough to have memory issues,
determinants are already completely infeasible. So I don't think anything
would be lost by the one-line change proposed by William. Of course,
writing a sparse algorithm that is competitive speed-wise, or could be
used only for very large matrices, would be ideal. But it took me some
time today to figure out why computing ~1000 determinants of 8x8 sparse
matrices was taking so long, and if there could be a quick fix to spare
others from my pain, it would be nice. :)
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/5402#comment:2>
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