On Dec 15, 2011, at 9:09 AM, Joao Amaral wrote: > Strangely(?), in both my laptop and the cluster, the number of threads from > the command > > call MPI_Comm_size ( MPI_COMM_WORLD, p, error )
Did you really mean "threads" there? Open MPI is process-parallel, meaning that calling COMM_SIZE on a communicator will return the number of *processes* in that communicator, not threads. See the man page for mpirun(1) for how to launch multiple processes in a single MPI job. Quick example: mpirun --hostfile your_host_file -np 8 your_mpi_program where: your_host_file: a file listing the host names to launch on 8: number of copies of your_mpi_program to launch your_mpi_program: your compiled executable MPI application -- Jeff Squyres jsquy...@cisco.com For corporate legal information go to: http://www.cisco.com/web/about/doing_business/legal/cri/