On Sunday 18 May 2008, Bill Hart wrote: > I don't have the two Gray code tables, so it would be good to get your > version. Also my code is currently a mess, so it would be good to > clean it up by merging with a cleaner version (yours). Tomorrow I'll > check carefully what I've changed and try and merge the ideas if there > are any you don't have which definitely improve performance on the > Opteron. > > The speedups I am seeing from the ifs are possibly a feature of the > Opteron cache algorithms. It is very sensitive when things just begin > to fall out of cache, as they certainly are here. Not combining with > the zero row just nudges things closer in to the cache boundary since > it never has to read that row. > > I have checked and the speedups are quite reproducible, and they > definitely come from the ifs, though I am now using a crossover with > Strassen of 7200!!
I'm using a crossover of 2048 here, so maybe our improvements are orthogonal? Even more puzzling, I'd expect that my crossover should be bigger than yours. (on a side note: my code changes how the crossover is used, your version: 'size < cutoff', my version: '|cutoff - size| is minimal' which should give a actual cutoffs closer to the desired values). My version is here: http://sage.math.washington.edu/home/malb/spkgs/libm4ri-20080516.p1.spkg (this needs an updated patch for Sage) and here: http://sage.math.washington.edu/home/malb/m4ri-20080516.tar.gz (which is the raw source). Those don't have SSE2 yet but it doesn't seem to make that much of a difference anyway. I'll add that back before doing an official release. However, unfortunately I'll probably have limited/no time tomorrow to commit. Martin PS: To give at least some indication that my code still does the right thing, a 'known answer' test: sage: A = random_matrix(GF(2), 10^3, 10^3) sage: B = random_matrix(GF(2), 10^3, 10^3) sage: (A*B)._magma_() == A._magma_() * B._magma_() True sage: (A._multiply_strassen(B,cutoff=256))._magma_() == A._magma_() * B._magma_() True -- name: Martin Albrecht _pgp: http://pgp.mit.edu:11371/pks/lookup?op=get&search=0x8EF0DC99 _www: http://www.informatik.uni-bremen.de/~malb _jab: [EMAIL PROTECTED] --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-devel@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sage-devel URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
