MPI processes in cosmomc

[Steven Pediani]

I have compiled cosmomc with MPICH2 in order to run on a cluster, but when I run the command,

mpirun -np 4 ./cosmomc params.ini,

The code only works out one chain. The output should say something like:

Number of MPI processes: 4, but instead says:

Number of MPI processes: 1
Number of MPI processes: 1
Number of MPI processes: 1
Number of MPI processes: 1

This results in only one chain being produced.

I've also tried using a PBS script, setting up the number of nodes, and processors per node, and although the code runs on all processors, I still only get one chain? Does anyone know how I can get it to compute 1 chain per node?

[Steven Pediani]

It appears that the problem was something to do with multiple mpirun.exe files being on the cluster.

[Pascal Vaudrevange]

Hi Steven,

depending on the MPI installation, you need to run lamboot before running mpirun.

Pascal

[Steven Pediani]

We seem to have sorted this now. If anyone runs into a similar problem, check you're using the mpiexec file from the same folder that you compiled with. I was compiling with MPICH2, but unknown to me, there was a some other mpi program installed on the cluster meaning mpiexec didn't correspond to MPICH2.