Compute Canada

How do I run parallel code?

Please note: The FAQ pages at the HPCVL website are continuously being revised. Some pages might pertain to an older configuration of the system. Please let us know if you encounter problems or inaccuracies, and we will correct the entries.

That depends on how the code is "parallelized". If it was "multi-threaded" by the compiler (automatic or via compiler directives), it is usually enough to set the environment variable PARALLEL or OMP_NUM_THREADS to the number of threads that should be used.

If it is MPI code, a special parallel runtime environment has to be used. The command there is mprun, which has command-line options that let you tell how many and which processors to use. This command is part of the CRE (Cluster Runtime Environment). CRE involves a good deal of commands that let you submit, cancel and check jobs that use MPI. The settings for this are included in our default setup.