I've heard this from a couple of other sources - it looks like there is a problem on the daemons when they compute the location for -cpus-per-proc. I'm not entirely sure why that would be as the code is supposed to be common with mpirun, but there are a few differences.
I will take a look at it - I don't know of any workaround, I'm afraid. On Mar 21, 2013, at 12:01 PM, Gus Correa <g...@ldeo.columbia.edu> wrote: > Dear Open MPI Pros > > I am having trouble using mpiexec with --cpus-per-proc > on multiple nodes in OMPI 1.6.4. > > I know there is an ongoing thread on similar runtime issues > of OMPI 1.7. > By no means I am trying to hijack T. Mishima's questions. > My question is genuine, though, and perhaps related to his. > > I am testing a new cluster remotely, with monster > dual socket 16-core AMD Bulldozer processors (32 cores per node). > I am using OMPI 1.6.4 built with Torque 4.2.1 support. > > I read that on these processors each pair of cores share an FPU. > Hence, I am trying to run *one MPI process* on each > *pair of successive cores*. > This trick seems to yield better performance > (at least for HPL/Linpack) than using all cores. > I.e., the goal is to use "each other core", or perhaps > to allow each process to wobble across two successive cores only, > hence granting exclusive use of one FPU per process. > [BTW, this is *not* an attempt to do hybrid MPI+OpenMP. > The code is HPL with MPI+BLAS/Lapack and NO OpenMP.] > > To achieve this, I am using the mpiexec --cpus-per-proc option. > It works on one node, which is great. > However, unless I made a silly syntax or arithmetic mistake, > it doesn't seem to work on more than one node. > > For instance, this works: > > #PBS -l nodes=1:ppn=32 > ... > mpiexec -np 16 \ > --cpus-per-proc 2 \ > --bind-to-core \ > --report-bindings \ > --tag-output \ > > I get a pretty nice process-to-cores distribution, with 16 processes, and > each process bound to a couple of successive cores, > as expected: > > [1,7]<stderr>:[node33:04744] MCW rank 7 bound to socket 0[core 14-15]: [. . . > . . . . . . . . . . . B B][. . . . . . . . . . . . . . . .] > [1,8]<stderr>:[node33:04744] MCW rank 8 bound to socket 1[core 0-1]: [. . . . > . . . . . . . . . . . .][B B . . . . . . . . . . . . . .] > [1,9]<stderr>:[node33:04744] MCW rank 9 bound to socket 1[core 2-3]: [. . . . > . . . . . . . . . . . .][. . B B . . . . . . . . . . . .] > [1,10]<stderr>:[node33:04744] MCW rank 10 bound to socket 1[core 4-5]: [. . . > . . . . . . . . . . . . .][. . . . B B . . . . . . . . . .] > [1,11]<stderr>:[node33:04744] MCW rank 11 bound to socket 1[core 6-7]: [. . . > . . . . . . . . . . . . .][. . . . . . B B . . . . . . . .] > [1,12]<stderr>:[node33:04744] MCW rank 12 bound to socket 1[core 8-9]: [. . . > . . . . . . . . . . . . .][. . . . . . . . B B . . . . . .] > [1,13]<stderr>:[node33:04744] MCW rank 13 bound to socket 1[core 10-11]: [. . > . . . . . . . . . . . . . .][. . . . . . . . . . B B . . . .] > [1,14]<stderr>:[node33:04744] MCW rank 14 bound to socket 1[core 12-13]: [. . > . . . . . . . . . . . . . .][. . . . . . . . . . . . B B . .] > [1,15]<stderr>:[node33:04744] MCW rank 15 bound to socket 1[core 14-15]: [. . > . . . . . . . . . . . . . .][. . . . . . . . . . . . . . B B] > [1,0]<stderr>:[node33:04744] MCW rank 0 bound to socket 0[core 0-1]: [B B . . > . . . . . . . . . . . .][. . . . . . . . . . . . . . . .] > [1,1]<stderr>:[node33:04744] MCW rank 1 bound to socket 0[core 2-3]: [. . B B > . . . . . . . . . . . .][. . . . . . . . . . . . . . . .] > [1,2]<stderr>:[node33:04744] MCW rank 2 bound to socket 0[core 4-5]: [. . . . > B B . . . . . . . . . .][. . . . . . . . . . . . . . . .] > [1,3]<stderr>:[node33:04744] MCW rank 3 bound to socket 0[core 6-7]: [. . . . > . . B B . . . . . . . .][. . . . . . . . . . . . . . . .] > [1,4]<stderr>:[node33:04744] MCW rank 4 bound to socket 0[core 8-9]: [. . . . > . . . . B B . . . . . .][. . . . . . . . . . . . . . . .] > [1,5]<stderr>:[node33:04744] MCW rank 5 bound to socket 0[core 10-11]: [. . . > . . . . . . . B B . . . .][. . . . . . . . . . . . . . . .] > [1,6]<stderr>:[node33:04744] MCW rank 6 bound to socket 0[core 12-13]: [. . . > . . . . . . . . . B B . .][. . . . . . . . . . . . . . . .] > > > *************** > > However, when I try to use eight nodes, > the job fails and I get the error message below (repeatedly from > several nodes): > > #PBS -l nodes=8:ppn=32 > ... > mpiexec -np 128 \ > --cpus-per-proc 2 \ > --bind-to-core \ > --report-bindings \ > --tag-output \ > > > Error message: > > -------------------------------------------------------------------------- > An invalid physical processor ID was returned when attempting to bind > an MPI process to a unique processor on node: > > Node: node18 > > This usually means that you requested binding to more processors than > exist (e.g., trying to bind N MPI processes to M processors, where N > > M), or that the node has an unexpectedly different topology. > > Double check that you have enough unique processors for all the > MPI processes that you are launching on this host, and that all nodes > have identical topologies. > > You job will now abort. > -------------------------------------------------------------------------- > > Oddly enough, the binding map *is* shown on STDERR, > and it sounds *correct*, pretty much the same binding map above > that I get for a single node. > > ***************** > > Finally, replacing "--cpus-per-core 2" by "--npernode 16" > works to some extent, but doesn't reach my goal. > I.e., the job doesn't fail, and each node gets 16 MPI > processes indeed. > However, it doesn't bind the processes the way I want. > Regardless of whether I continue to use "--bind-to-core" > or replace it by "--bind-to-socket" > all 16 processes on each node always bind to socket 0, > and nothing goes to socket 1. > > ************ > > Is there any simple workaround to this > (other than using a --rankfile), > to make --cpus-per-proc work with multiple nodes, > using "each other core"? > > [Only if it is simple workaround. I must finish this > remote test soon. Otherwise I can revisit this issue later.] > > Thank you, > Gus Correa > > > > > > _______________________________________________ > users mailing list > us...@open-mpi.org > http://www.open-mpi.org/mailman/listinfo.cgi/users
