My MPI application hangs on startup.

Symptoms

If your application has both of the following symptoms:

1. works on a low number of nodes, but hangs on startup on higher node counts
2. works with ethernet (by setting --mca btl ^openib on the mpirun command), but not with infiniband

Then try to revert back to OpenMPI 1.2.4 by setting this before recompiling and in your job script:

module unload openmpi
module load openmpi/1.2.4
module load intel-compiler

Please tell us if this helps for you application. We try to get an idea of the extent of this problem. Send a report to support-uit@notur.no.