| Damien Robert on Fri, 07 Sep 2012 14:01:48 +0200 |
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| matdet regression |
This comes from the Sage Mailing List: https://groups.google.com/forum/?fromgroups=#!topic/sage-devel/uneXpZnRs-U G = graphs.OddGraph(4) M=G.kirchhoff_matrix() M.subdivide(1,1) M2 = M.subdivision(1,1) time M2._det_pari(1) #classical Gaussian elimination -> 0sec time M2._det_pari(0) #Gauss-Bareiss -> 8 minutes Interestingly enough, when I try it on Sage 4.7 both versions are instantaneous. It is only starting with Sage 4.8 that the regression happens. The matrix is the following one: m2=[\ 4,1,0,0,0,0,0,1,1,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;\ -1,4,0,0,0,0,0,0,0,1,0,0,0,0,0,0,1,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;\ 0,0,4,0,0,0,1,0,0,0,1,1,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;\ 0,0,0,4,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,1,1;\ 0,0,0,0,4,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,1,1,0,0,0,0,0,0,0,0,0,1,0,0;\ 0,0,0,0,0,4,0,0,0,0,0,0,0,1,0,1,0,0,0,0,1,0,0,1,0,0,0,0,0,0,0,0,0,0;\ 0,0,1,0,0,0,4,0,0,0,0,0,0,0,0,0,0,1,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,1;\ -1,0,0,0,0,0,0,4,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,1,0,1;\ -1,0,0,0,0,0,0,0,4,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,0,0,0;\ 0,1,0,0,1,0,0,0,0,4,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,0,0,0;\ 0,0,1,0,0,0,0,0,1,0,4,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,1,0,0,0,0,0,0,0;\ 0,0,1,0,0,0,0,0,0,0,0,4,0,1,0,0,0,0,1,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0;\ 0,0,1,0,0,0,0,0,0,0,0,0,4,0,0,0,1,0,0,0,0,1,1,0,0,0,0,0,0,0,0,0,0,0;\ -1,0,0,0,0,1,0,0,0,0,0,1,0,4,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0;\ 0,0,0,0,0,0,0,0,0,0,0,0,0,0,4,0,0,0,0,0,0,0,1,0,1,0,0,1,0,1,0,0,0,0;\ 0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,4,1,0,0,0,0,0,0,0,0,-1,1,0,0,0,0,0,0,0;\ 0,1,0,0,0,0,0,0,0,0,0,0,1,0,0,1,4,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;\ 0,1,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,4,0,0,0,0,0,0,1,0,0,0,1,0,0,0,0,0;\ 0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,4,0,0,0,0,0,0,0,0,0,1,0,0,1,0,0;\ 0,0,0,1,0,0,0,0,0,1,1,0,0,0,0,0,0,0,0,4,0,0,0,1,0,0,0,0,0,0,0,0,0,0;\ 0,0,0,0,1,1,1,0,0,0,0,0,0,0,0,0,0,0,0,0,4,0,0,0,0,0,0,0,0,1,0,0,0,0;\ 0,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,4,0,0,0,0,0,0,0,0,1,0,1,0;\ 0,0,0,0,0,0,0,1,0,0,0,0,1,0,1,0,0,0,0,0,0,0,4,1,0,0,0,0,0,0,0,0,0,0;\ 0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,1,4,0,0,0,0,1,0,0,0,0,0;\ 0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,1,0,0,0,0,0,0,4,0,1,0,0,0,0,0,1,0;\ 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,4,0,1,0,0,1,0,0,1;\ 0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,1,0,0,0,0,0,0,0,0,1,0,4,0,0,0,0,1,0,0;\ 0,0,0,0,0,0,0,0,0,1,0,1,0,0,1,0,0,0,0,0,0,0,0,0,0,-1,0,4,0,0,0,0,0,0;\ 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,0,0,0,0,1,0,0,0,0,4,0,1,0,0,0;\ 0,0,0,0,0,0,0,0,1,0,0,0,0,0,1,0,0,0,0,0,1,0,0,0,0,0,0,0,0,4,0,0,0,0;\ 0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,-1,0,0,1,0,4,0,0,0;\ 0,0,0,0,1,0,0,1,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,0,4,0,0;\ 0,0,0,1,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,1,0,0,1,0,0,0,0,0,0,0,4,0;\ 0,0,0,1,0,0,1,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,-1,0,0,0,0,0,0,0,4\ ] with GP/PARI CALCULATOR Version 2.5.1 (development git-34bc885) matdet(m2,flag=0) is much slower than matdet(m2,flag=1)