[mpich-discuss] new to mpi: performance issues when using mpich

[Raffenetti, Ken]

--cpus-per-task is not equivalent to -ppn when using mpiexec/mpirun. -ppn says launch this many processes per node. --cpus-per-tasks says launch as many processes as you can so that each has access to at least 8 CPU cores. Trying tuning the launch options so you are sure you are launching the same number of procs in either configuration.

Ken

On 2/16/22, 12:36 PM, "Sopena Ballesteros Manuel via discuss" <discuss at mpich.org> wrote:

    I am learning how to install and run mpi aplications. My goal is to install mpich and run osu micro benchmark in order to understand how it works.

    so far I got it working but I must be doing wrong because the latency tests does not looks right to me.

    /scratch/e1000/msopena/mpich-installed/bin/mpirun -f /scratch/e1000/msopena/hosts -ppn 8 /scratch/e1000/msopena/osu-micro-benchmarks-5.8/mpi/collective/osu_alltoall

    # OSU MPI All-to-All Personalized Exchange Latency Test v5.8
    # Size       Avg Latency(us)
    1                     104.87
    2                     101.44
    4                     105.47
    8                      94.35
    16                     95.14
    32                    239.45
    64                    293.59
    128                   437.93
    256                   414.21
    512                   444.74
    1024                  655.93
    2048                  529.20
    4096                  551.84
    8192                  574.99
    16384                 644.90
    32768                 790.70
    65536                4169.19
    131072               4756.38
    262144               6782.57
    524288              12299.24
    1048576             22880.86


    However, I get notmal results when the osu benchmarks through srun

    eg
    $ srun -N3 --cpus-per-task=8 /scratch/e1000/msopena/osu-micro-benchmarks-5.8/mpi/collective/osu_alltoall

    # OSU MPI All-to-All Personalized Exchange Latency Test v5.8
    # Size       Avg Latency(us)
    1                      27.43
    2                      27.97
    4                      29.26
    8                      30.69
    16                     31.77
    32                     34.89
    64                     42.06
    128                    60.83
    256                   115.84
    512                   205.33
    1024                  282.61
    2048                  446.41
    4096                  733.10
    8192                 1421.99
    16384                2832.45
    32768                5631.33
    65536               11242.08
    131072              22645.46
    262144              45544.75
    524288              90440.93
    1048576            186709.32


    Could someone please help me to troubleshoot could be wrong when I use mpich stand alone? 


    thank you very much