User`s guide

Intel® MPI Library User’s Guide for Linux* OS

#PBS -l walltime=1:30:00

#PBS -q workq

#PBS -V

# Set Intel MPI environment

mpi_dir=<installdir>/<arch>/bin

cd $PBS_O_WORKDIR

source $mpi_dir/mpivars.sh

# Launch application

mpirun -n <# of processes> ./myprog

2. Submit the job using the PBS qsub command:

$ qsub pbs_run.sh

When using mpirun under a job scheduler, you do not need to determine the number of available

nodes. Intel MPI Library automatically detects the available nodes through the Hydra process

manager.

2.8. Controlling MPI Process Placement

The mpirun command controls how the ranks of the processes are allocated to the nodes

of the cluster. By default, the mpirun command uses group round-robin assignment,

putting consecutive MPI process on all processor ranks of a node. This placement

algorithm may not be the best choice for your application, particularly for clusters with

symmetric multi-processor (SMP) nodes.

Suppose that the geometry is <#ranks> = 4 and <#nodes> = 2, where adjacent pairs of

ranks are assigned to each node (for example, for two-way SMP nodes). To see the

cluster nodes, enter the command:

cat ~/mpi_hosts

The results should look as follows:

clusternode1

clusternode2

To equally distribute four processes of the application on two-way SMP clusters, enter the

following command:

mpirun –perhost 2 –n 4 ./myprog.exe

The output for the myprog.exe executable file may look as follows:

Hello world: rank 0 of 4 running on clusternode1