[CP2K:3705] hwloc support in cp2k-trunk

Christiane Pousa pousa.ch... at gmail.com
Mon Jan 23 07:59:49 UTC 2012

Hi Axel,

I'm Christiane and the one responsible for the hwloc/libnuma support on

Concerning libnuma, the affinity support is much simpler than the one with
hwloc. Only, thread/process affinity. I'll check this wrapper to see why it
is not working and let you know.

About hwloc, that is true that it requires the latest version because of
the pci support for network cards and gpus. By default this module, only
attach processes and their memory to NUMA nodes. Their threads are not
pinned to any cores, so they can move within a NUMA node. There are other
strategies to place MPI/threads that can be used by setting the
machine_arch keys.

Could you send me the input, machine_arch keys that you used for these
tests? I've tested hwloc support on local intel/amd machines (with and
without gpus) and on CRAY machines and I have no errors like that. All of
them with NUMA characteristics.

When you use numactl, how do you can determine the cores for threads and
MPI tasks? Do you attribute processes to NUMA nodes and consequently,
threads are also attached to the same set of cores of their parent?

So, if you have any suggestions, comments, we can discuss this and also
solve the problems that you have found.

Christiane Pousa Ribeiro
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