Hi, Can comm_spawn be used with win_create. For ex: Master process: MPI_Comm_spawn(worker_program,MPI_ARGV_NULL, world_size-1, info, 0, MPI_COMM_SELF, &everyone, MPI_ERRCODES_IGNORE); MPI_Win_create(&testval, sizeof(double), 1, MPI_INFO_NULL, everyone, &nwin); Worker process: MPI_Comm_get_parent(&parent); if (parent == MPI_COMM_NULL) error("No parent!"); MPI_Comm_remote_size(parent, &size); if (size != 1) error("Something's wrong with the parent"); fprintf (stdout,"Size: %zd\n", size); system("echo $NUM_THREADS"); MPI_Win_create(MPI_BOTTOM, 0, 1, MPI_INFO_NULL, parent, &nwin); This one fails currently. Am I doing something wrong. It would be great if someone could help me. Thanks Ramesh