MPI_Send_init (buf0, buf_size, MPI_INT, 1, 0, MPI_COMM_WORLD, &aReq[0]);
MPI_Recv_init (buf1, buf_size, MPI_INT, 1, 0, MPI_COMM_WORLD, &aReq[1]);
MPI_Send_init (buf0, buf_size, MPI_INT, 1, 0, MPI_COMM_WORLD, &aReq[0]);
MPI_Recv_init (buf1, buf_size, MPI_INT, 1, 0, MPI_COMM_WORLD, &aReq[1]);