I do agree that we should use a parallel blas whenever possible, I just wanted to give the rationale why atlas defaults to single-threaded ;-)
On Tuesday, March 27, 2012 2:48:15 PM UTC+1, William wrote: > > On Tue, Mar 27, 2012 at 2:39 PM, Volker Braun <vbraun.n...@gmail.com> > wrote: > > The current state is that we build static atlas with and without threads, > > and the shared library without threads only. And our module_list.py links > > with the single-threaded atlas shared library only. So Sage will use the > > single-threaded version if you build atlas yourself. > > > > If you use the os-provided atlas library (which can be multi-threaded yet > > not have the "pt" in the name), you get parallel atlas. For example, on > > Fedora I'm using the system atlas and get > > > > sage: sage: a = random_matrix(RDF,1000) > > sage: time a*a > > 1000 x 1000 dense matrix over Real Double Field > > Time: CPU 1.08 s, Wall: 0.26 s > > > > And if anybody wonders why there is a single-threaded atlas at all: > People > > often specifically WANT a single-threaded blas, and implement their own > > parallelism on top of that. > > I WANT a multithreaded atlas in Sage :-) > > -- William > > > > > > > > > > > On Tuesday, March 27, 2012 2:14:26 PM UTC+1, William wrote: > >> > >> On Tue, Mar 27, 2012 at 12:39 PM, Volker Braun <vbraun.n...@gmail.com> > >> wrote: > >> > When I rewrote the atlas spkg I enabled multithreaded atlas libraries. > >> > That > >> > is, we configure atlas to allow threading. Whether or not atlas > actually > >> > builds threaded libraries depends on os and configure checks for > >> > ptthreads. > >> > >> Does it work on mod.math.washington.edu? I tried > >> > >> sage: a = random_matrix(RDF,1000) > >> sage: time b = a*a > >> Time: CPU 0.43 s, Wall: 0.43 s > >> > >> and clearly ATLAS is *NOT* being multithreaded. > >> However, if I do the same on my little OS X laptop, I get: > >> > >> sage: a = random_matrix(RDF,1000) > >> sage: time b = a*a > >> Time: CPU 0.45 s, Wall: 0.13 s # <--- look at that walltime! > >> > >> which is clearly multithreaded. > >> > >> - William > >> > >> > > >> > -- > >> > To post to this group, send an email to sage-devel@googlegroups.com > >> > To unsubscribe from this group, send an email to > >> > sage-devel+unsubscr...@googlegroups.com > >> > For more options, visit this group at > >> > http://groups.google.com/group/sage-devel > >> > URL: http://www.sagemath.org > >> > >> -- > >> William Stein > >> Professor of Mathematics > >> University of Washington > >> http://wstein.org > > > > -- > > To post to this group, send an email to sage-devel@googlegroups.com > > To unsubscribe from this group, send an email to > > sage-devel+unsubscr...@googlegroups.com > > For more options, visit this group at > > http://groups.google.com/group/sage-devel > > URL: http://www.sagemath.org > > -- > William Stein > Professor of Mathematics > University of Washington > http://wstein.org > > -- To post to this group, send an email to sage-devel@googlegroups.com To unsubscribe from this group, send an email to sage-devel+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URL: http://www.sagemath.org
