>> On 04-01-2013 18:28, Ralph Castain wrote: >>> FWIW: I believe we have a mapper in Open MPI that does what you want - >>> i.e., it looks at the number of available cpus on each node, and maps the >>> processes to maximize the number of procs co-located on nodes. In your >>> described case, it would tend to favor the 16ppn nodes as that would >>> provide the best MPI performance, then move to the 8ppn nodes, etc. >> >> Yes, OpenMPI can be tweaked into different task layouts on the available set >> of >> nodes. But the problem at hand is for the scheduler to allocate some set of >> nodes, given that the user want a specific number of MPI tasks (say, 32), and >> given that there are heterogeneous nodes available with 4, 8 or 16 cores. As >> Moe wrote, this flexibility would be hard to achieve with Slurm (with Maui >> it's >> impossible). > > I think you may have misunderstood both Moe and I. I believe Moe was pointing > out that you would need a new plugin to provide that capability, and I > pointed out that we already have that algorithm in OMPI and could port it to > a Slurm plugin if desired. That said, it would take some time to make that > happen, so it may not resolve your problem.
Thanks for enlightening me! Sounds interesting, and may be worth a future effort because so many clusters are (or will become) heterogeneous! Regards, Ole
