SGI Altix Message Passing FAQ

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• Where are the commands to compile my MPI program (mpicc, mpif90, etc.)?
• The following error occurrs when I run a MPI program: mpirun: Please limit mpi test and debug runs to -np 4 or less. Is this because my account is set up only for that? When I login to cobalt.ncsa.uiuc.edu, I can only login to co-login1. How can I submit a job to larger number of processors?
• I need to submit a MPI-OpenMP hybrid job on Cobalt. Do you have a sample PBS script for the same.

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Where are the commands to compile my MPI program (mpicc, mpif90, etc.)?

The usual commands for compiling MPI programs (mpicc, mpif77, mpif90, etc.) are not available on the SGI Altix. To find out how to compile your MPI program, see NCSA's SGI Altix Programming Environment web page.

The following error occurrs when I run a MPI program: mpirun: Please limit mpi test and debug runs to -np 4 or less. Is this because my account is set up only for that? When I login to cobalt.ncsa.uiuc.edu, I can only login to co-login1. How can I submit a job to larger number of processors?

To run an MPI program on more than 4 processors, you need to run the MPI program within a batch job. For information about batch jobs, see: batch jobs web page. For information about interactive jobs, see the interactive jobs web page.

I need to submit a MPI-OpenMP hybrid job on Cobalt. Do you have a sample PBS script for the same.

You may consider using the online sample mpi batch script (/usr/local/doc/pbs/samples/mpi.pbs) with the following changes:
• list the total cpus (MPI_processes * OpenMP_threads) in the PBS -l ncpus directive
• set the environment variable OMP_NUM_THREADS to the number of OpenMP threads
• explicitly set the number of MPI processes in the -np argument to mpirun