MPI_Sendrecv(buffer, 10, MPI_INT, left, TAG_SND, buffer2, 10, MPI_INT, right, TAG_RCV, MPI_COMM_WORLD, &status);
for (i=0;i<BUFLEN;i++) {
MPI_Sendrecv(buffer, 10, MPI_INT, left, TAG_SND, buffer2, 10, MPI_INT, right, TAG_RCV, MPI_COMM_WORLD, &status);
for (i=0;i<BUFLEN;i++) {