Dear MPI users, Recently I moved to Ubuntu 13.10 and I got a problem with running my codes on ubutnu 13.10. After checking my code I tried to execute a hello world! code instead to make sure that the problem is from mpi or not. Then I find that rank of all processes is 0 and size is 1 independent from the number of processes that I use with mpiexec. herer is the code: #include <mpi.h> #include <iostream> using namespace std; int main(int argc ,char ** argv) { int size,rank; MPI_Init(&argc, &argv); MPI_Comm_size(MPI_COMM_WORLD, &size); MPI_Comm_rank(MPI_COMM_WORLD, &rank); cout<<rank<<endl; MPI_Finalize(); } Is there any thing wrong with this code? Thanks in advance, Ehsan