Jeff Thanks, this is helpful. I am mostly interested in finding out which threads share the D1 cache. I guess that get_bgq_core returns this information.
Is there a way to guarantee that this association doesn't change at run time? I guess I could just check periodically... -erik On Tue, Jan 8, 2013 at 5:33 PM, Jeff Hammond <jhamm...@alcf.anl.gov> wrote: > As a temporary, non-portable substitute for hwloc, you can use the SPI > calls that are described on my Wiki: > https://wiki.alcf.anl.gov/parts/index.php/Blue_Gene/Q#Node_topology. > I presume that this is the means by which hwloc will support BGQ when > it does. > > Blue Gene/Q has 16+1 cores with 4 hw threads each. Only 16 cores are > visible to applications but as users can, in theory, run code on the > 17th core (see > https://wiki.alcf.anl.gov/parts/index.php/Blue_Gene/Q#17th_Core_App_Agents > for how), it is important for these functions to return values in the > range 0..16 and 0..67 instead of 0..15 and 0..63. I include this > information in case users are confused about the additional range > documented for these calls. > > Best, > > Jeff > > On Tue, Jan 8, 2013 at 11:10 AM, Brice Goglin <brice.gog...@inria.fr> > wrote: > > Hello Erik, > > We need specific BGQ binding support, the binding API is different. Also > we > > don't properly detect the 16 4-way cores properly, we only only 64 > identical > > PUs. > > I am supposed to get a BGQ account in the near future so I hope I will > have > > everything working in v1.7. > > Stay tuned > > Brice > > > > > > > > > > Le 08/01/2013 18:06, Erik Schnetter a écrit : > > > > I am trying to use hwloc on a Blue Gene/Q. Building and installing worked > > fine, and it reports the system configuration fine as well (i.e. it shows > > all PUs). However, when I try to inquire the thread/core bindings, hwloc > > crashes with an error in libc's free(). This is both with 1.6 and > 1.6.1rc1. > > > > The error occurs apparently in CPU_FREE called from > > hwloc_linux_find_kernel_nr_cpus. > > > > Does this ring a bell with anyone? I know this is not enough information > to > > debug things, but do you have any pointers for things to look at? > > > > I remember reading somewhere that the last bit in a cpu_set_t cannot be > > used. A Blue Gene/Q has 64 PUs, and may be using 64-bit integers to hold > > cpu_set_t data. Could this be an issue? > > > > My goal is to examine and experiment with thread/core bindings with > OpenMP > > to improve performance. > > > > -erik > > > > -- > > Erik Schnetter <schnet...@gmail.com> > > http://www.perimeterinstitute.ca/personal/eschnetter/ > > > > > > _______________________________________________ > > hwloc-users mailing list > > hwloc-us...@open-mpi.org > > http://www.open-mpi.org/mailman/listinfo.cgi/hwloc-users > > > > > > > > _______________________________________________ > > hwloc-users mailing list > > hwloc-us...@open-mpi.org > > http://www.open-mpi.org/mailman/listinfo.cgi/hwloc-users > > > > -- > Jeff Hammond > Argonne Leadership Computing Facility > University of Chicago Computation Institute > jhamm...@alcf.anl.gov / (630) 252-5381 > http://www.linkedin.com/in/jeffhammond > https://wiki.alcf.anl.gov/parts/index.php/User:Jhammond > > _______________________________________________ > hwloc-users mailing list > hwloc-us...@open-mpi.org > http://www.open-mpi.org/mailman/listinfo.cgi/hwloc-users > -- Erik Schnetter <schnet...@cct.lsu.edu> http://www.perimeterinstitute.ca/personal/eschnetter/
