= Source code =
{{{
/* Program:
 *   每個 node 將自己的 id 資訊送給下一個 node。
 * History:
 *   2008-06-05 BETA
 *   2008-06-06 改變 #30 printf 位置，以了解 MPI 函式執行順序關係
 *   2008-06-12 更改顯示方法。
 *   2008-06-17 變更變數名 myid -> myrank，增加註解
 */

#include <mpi.h>
#include <stdio.h>

main(int argc,char **argv)     
{
  int n, myrank, numprocs;
  MPI_Status status;
  MPI_Init(&argc,&argv);
  MPI_Comm_size(MPI_COMM_WORLD,&numprocs);
  MPI_Comm_rank(MPI_COMM_WORLD,&myrank);

  /* node 0 will send the first message */
  if(myrank == 0)
  {
    n = myrank;
    MPI_Send(&n, 1, MPI_INT, 1, 99, MPI_COMM_WORLD);
    printf("[Ndde %d]「%d」 >> [Node %d]\n\n", myrank, n, myrank+1);
  }

  /* node 1 to node n-2 will send message to the next node */
  if(myrank>0 && myrank<numprocs-1)
  {
    MPI_Recv(&n, 1, MPI_INT, myrank-1, 99, MPI_COMM_WORLD, &status);
    printf("[Node %d] << 「%d」[Node %d]\n", myrank, n, status.MPI_SOURCE);
    n = myrank;
    MPI_Send(&n, 1, MPI_INT, myrank+1, 99, MPI_COMM_WORLD);
    printf("[Ndde %d]「%d」 >> [Node %d]\n\n", myrank, n, myrank+1);
  }

  /* the final node n-1 will not send any message but receive*/
  if(myrank==numprocs-1)
  {
    MPI_Recv(&n, 1, MPI_INT, myrank-1, 99, MPI_COMM_WORLD, &status);
    printf("[Node %d] << 「%d」[Node %d]\n", myrank, n, status.MPI_SOURCE);
  }
  MPI_Finalize();
}
}}}
= Result =
[[Image(demo2-01.png)]]