Running MPI program on hydra

Run program directly with mpirun


mpirun  --display-map -H <host1,host2,…> -np <# processes>  /path/to/myprogram arg1 arg2


--display-map: Display the process map just before launch.

-H :
specifies nodes for your program to run on.

        <host1,host2,…> is replaced by compute node names.

Use n0,n1,n2,…n15 to indicate the compute nodes.

-np: run n copies of the program on the given nodes. The given nodes are specified by -H parameter.

       Usually np cannot be greater than the number of cores of the given node.

mpirun  --display-map -H n0,n1 -np 24 ./cge-mpi1 48

The command will run cge-mpi1 using matrix size 48 and it distributes the processing among 2 nodes (n0,n1) and 24 processors (each node will use 12 cores).