VPAC Systems Blog

Due to scaling problems we have found in the default version of MPI on Tango (MVAPICH2) we have had to replace it. Jobs of larger than 64 processors would not start.

It has been replaced by OpenMPI v1.2.4 which is the successor to the older LAM-MPI and has full Infiniband support and much better debugging information should a job fail.

We have today switched the default MPI over to this version, so please, if you use MPI programs on Tango, recompile them!

You can see which versions of OpenMPI are available with the command:

module avail openmpi

The current default is for the Portland Group compiler, but should you wish to pick one that uses GCC or the Intel compilers you will need to do:

module load openmpi/1.2.4-gcc

or

module load openmpi/1.2.4-intel

Remember that you will need to insert the same statement into your PBS script before launching your job!

To launch an OpenMPI process from a PBS script just do:

mpiexec ./my-program [arguments]