Developer Guide

Running an MPI Program

Before running an MPI program, place it to a shared location and make sure it is accessible from all cluster nodes. Alternatively, you can have a local copy of your program on all the nodes. In this case, make sure the paths to the program match.
Run the MPI program using the
mpiexec
command. The command line syntax is as follows:
> mpiexec -n <number-of-processes> -ppn <processes-per-node> -f <hostfile> myprog.exe
For example:
> mpiexec -n 4 -ppn 2 -f hosts myprog.exe
The
mpiexec
command launches the Hydra process manager, which controls the execution of your MPI program on the cluster.
In the command line above:
  • -n
    sets the number of MPI processes to launch; if the option is not specified, or uses the number of cores on the machine.
  • -ppn
    sets the number of processes to launch on each node; if the option is not specified, processes are assigned to the physical cores on the first node; if the number of cores is exceeded, the next node is used.
  • -f
    specifies the path to the host file listing the cluster nodes; alternatively, you can use the
    -hosts
    option to specify a comma-separated list of nodes; if hosts are not specified, the local node is used.
  • myprog
    .exe
    is the name of your MPI program.
For the list of all available options, run
mpi
exec
with the
-help
option, or see section mpiexec.hydra in the
Intel® MPI Library Developer Reference
.

Product and Performance Information

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Performance varies by use, configuration and other factors. Learn more at www.Intel.com/PerformanceIndex.