|Re: [sage-devel] Strange performance (bug?) computing a specific determinant||D. S. McNeil||06/09/12 08:03|
> That said, I am wondering if this is perhaps a bug in the default implementation of determinant()?
> It seems strange to me that it takes 8 minutes to compute a determinant of a 34x34 matrix while other algorithms do it within a second.
Yeah, it looks like pari's Gauss-Bareiss takes forever on this matrix,
even though its classical Gaussian is quick:
sage: time m2._det_pari(1)
Time: CPU 0.00 s, Wall: 0.00 s
sage: time m2._det_pari(0)
Time: CPU 597.13 s, Wall: 597.10 s
Kind of funny: _det_pari(0) is so slow on this particular matrix that
it's five orders of magnitude faster to square m2 and take the root of
sage: %timeit (m2)._det_pari(1)
125 loops, best of 3: 3.39 ms per loop
sage: %timeit (m2*m2)._det_pari(0)^(1/2)
125 loops, best of 3: 5.92 ms per loop
|Re: [sage-devel] Strange performance (bug?) computing a specific determinant||Jernej Azarija||06/09/12 14:03|
Interesting! I have also noticed that if I just slightly modify the matrix m2, it again works efficiently.
Will someone direct the pariGP guys to this issue?
|Re: Strange performance (bug?) computing a specific determinant||Jernej Azarija||02/01/13 09:11|
Has anyone already looked into this thing?
The bug appears to slow down all matrix computations related to pariGP. For example it gets stuck computing the eigenvalues of a matrix as well. It's quite annoying.
The pariGP guys confirmed it's a bug in pari so we should update the pari package that sage ships!
On Thursday, 6 September 2012 14:12:07 UTC+2, Jernej Azarija wrote:
Consider the following program
|Re: [sage-devel] Re: Strange performance (bug?) computing a specific determinant||Jeroen Demeyer||03/01/13 03:23|
On 2013-01-02 18:11, Jernej Azarija wrote:If you create a Sage ticket for this issue, pointing to the PARI/GP bug
report and cc: me, I'll happily apply the fix.
|Re: [sage-devel] Re: Strange performance (bug?) computing a specific determinant||Jeroen Demeyer||03/01/13 05:38|