On Tue, Oct 4, 2016 at 12:58 PM, Jonathan Bober <jwbo...@gmail.com> wrote: > No, in 7.3 Sage isn't multithreading in this example: > > jb12407@lmfdb1:~$ sage73 > sage: %time M = ModularSymbols(5113, 2, -1) > CPU times: user 599 ms, sys: 25 ms, total: 624 ms > Wall time: 612 ms > sage: %time S = M.cuspidal_subspace().new_subspace() > CPU times: user 1.32 s, sys: 89 ms, total: 1.41 s > Wall time: 1.44 s > > I guess the issue may be OpenBLAS rather than Linbox, then, since LinBox > uses BLAS. I misread https://trac.sagemath.org/ticket/21323, which I now > realize says "LinBox parallel routines (not yet exposed in SageMath)", when > I thought that the cause may be LinBox. My Sage 7.3. uses the system ATLAS, > and I don't know whether that might sometimes use multithreading.
If you care about performance you should build ATLAS from source. You can (somehow... I can't remember how) specify how many cores it will use, and it will greatly benefit from multithreading. > > > On Tue, Oct 4, 2016 at 8:06 PM, Francois Bissey > <francois.bis...@canterbury.ac.nz> wrote: >> >> openmp is disabled in linbox/ffpack-fflas so it must come from somewhere >> else. >> Only R seems to be linked to libgomp (openmp) on my vanilla install. >> Curiosity: do you observe the same behaviour in 7.3? >> >> François >> >> > On 5/10/2016, at 07:26, Jonathan Bober <jwbo...@gmail.com> wrote: >> > >> > See the following timings: If I start Sage with OMP_NUM_THREADS=1, a >> > particular computation takes 1.52 cpu seconds and 1.56 wall seconds. >> > >> > The same computation without OMP_NUM_THREADS set takes 12.8 cpu seconds >> > and 1.69 wall seconds. This is particularly devastating when I'm running >> > with @parallel to use all of my cpu cores. >> > >> > My guess is that this is Linbox related, since these computations do >> > some exact linear algebra, and Linbox can do some multithreading, which >> > perhaps uses OpenMP. >> > >> > jb12407@lmfdb1:~$ OMP_NUM_THREADS=1 sage >> > [...] >> > SageMath version 7.4.beta6, Release Date: 2016-09-24 >> > [...] >> > Warning: this is a prerelease version, and it may be unstable. >> > [...] >> > sage: %time M = ModularSymbols(5113, 2, -1) >> > CPU times: user 509 ms, sys: 21 ms, total: 530 ms >> > Wall time: 530 ms >> > sage: %time S = M.cuspidal_subspace().new_subspace() >> > CPU times: user 1.42 s, sys: 97 ms, total: 1.52 s >> > Wall time: 1.56 s >> > >> > >> > jb12407@lmfdb1:~$ sage >> > [...] >> > SageMath version 7.4.beta6, Release Date: 2016-09-24 >> > [...] >> > sage: %time M = ModularSymbols(5113, 2, -1) >> > CPU times: user 570 ms, sys: 18 ms, total: 588 ms >> > Wall time: 591 ms >> > sage: %time S = M.cuspidal_subspace().new_subspace() >> > CPU times: user 3.76 s, sys: 9.01 s, total: 12.8 s >> > Wall time: 1.69 s >> > >> > >> > -- >> > You received this message because you are subscribed to the Google >> > Groups "sage-devel" group. >> > To unsubscribe from this group and stop receiving emails from it, send >> > an email to sage-devel+unsubscr...@googlegroups.com. >> > To post to this group, send email to sage-devel@googlegroups.com. >> > Visit this group at https://groups.google.com/group/sage-devel. >> > For more options, visit https://groups.google.com/d/optout. >> >> -- >> You received this message because you are subscribed to the Google Groups >> "sage-devel" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to sage-devel+unsubscr...@googlegroups.com. >> To post to this group, send email to sage-devel@googlegroups.com. >> Visit this group at https://groups.google.com/group/sage-devel. >> For more options, visit https://groups.google.com/d/optout. > > > -- > You received this message because you are subscribed to the Google Groups > "sage-devel" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sage-devel+unsubscr...@googlegroups.com. > To post to this group, send email to sage-devel@googlegroups.com. > Visit this group at https://groups.google.com/group/sage-devel. > For more options, visit https://groups.google.com/d/optout. -- William (http://wstein.org) -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To post to this group, send email to sage-devel@googlegroups.com. Visit this group at https://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/d/optout.
