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. 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.
