Actually, if you look closely at the definition of those two values, you'll see that it really doesn't matter which one we loop over. The NUM_BITS value defines the actual total number of bits in the mask. The CPU_MAX is the total number of cpus we can support, which was set to a value such that the two are equal (i.e., it's a power of two that happens to be an integer multiple of 64).
I believe the original intent was to allow CPU_MAX to be independent of address-alignment questions, so NUM_BITS could technically be greater than CPU_MAX. Even if this happens, though, all that would do is cause the loop to run across more bits than required. So it doesn't introduce a limitation at all. In hindsight, we could simplify things by eliminating one of those values and just putting a requirement on the number that it be a multiple of 64 so it aligns with a memory address. On Aug 29, 2011, at 7:05 AM, Kenneth Lloyd wrote: > Nadia, > > Interesting. I haven't tried pushing this to levels above 8 on a particular > machine. Do you think that the cpuset / paffinity / hwloc only applies at > the machine level, at which time you need to employ a graph with carto? > > Regards, > > Ken > > -----Original Message----- > From: devel-boun...@open-mpi.org [mailto:devel-boun...@open-mpi.org] On > Behalf Of nadia.derbey > Sent: Monday, August 29, 2011 5:45 AM > To: Open MPI Developers > Subject: [OMPI devel] known limitation or bug in hwloc? > > Hi list, > > I'm hitting a limitation with paffinity/hwloc with cpu numbers >= 64. > > In opal/mca/paffinity/hwloc/paffinity_hwloc_module.c, module_set() is > the routine that sets the calling process affinity to the mask given as > parameter. Note that "mask" is a opal_paffinity_base_cpu_set_t (so we > allow the cpus to be potentially numbered up to > OPAL_PAFFINITY_BITMASK_CPU_MAX - 1). > > The problem with module_set() is that is loops over > OPAL_PAFFINITY_BITMASK_T_NUM_BITS bits to check if these bits are set in > the mask: > > for (i = 0; ((unsigned int) i) < OPAL_PAFFINITY_BITMASK_T_NUM_BITS; ++i) > { > if (OPAL_PAFFINITY_CPU_ISSET(i, mask)) { > hwloc_bitmap_set(set, i); > } > } > > Given "mask"'s type, I think module_set() should instead loop over > OPAL_PAFFINITY_BITMASK_CPU_MAX bits. > > Note that module_set() uses a type for its internal mask that is > coherent with OPAL_PAFFINITY_BITMASK_T_NUM_BITS (hwloc_bitmap_t). > > So I'm wondering whether this is a known limitation I've never heard of > or an actual bug? > > Regards, > Nadia > > > _______________________________________________ > devel mailing list > de...@open-mpi.org > http://www.open-mpi.org/mailman/listinfo.cgi/devel > ----- > No virus found in this message. > Checked by AVG - www.avg.com > Version: 10.0.1392 / Virus Database: 1520/3864 - Release Date: 08/28/11 > > _______________________________________________ > devel mailing list > de...@open-mpi.org > http://www.open-mpi.org/mailman/listinfo.cgi/devel
