| 46 | | ---- |
| 47 | | 有問題，為什麼 node 0 沒有 send 任何 message ，而其它的 node 卻能執行。怒…。 |
| 48 | | {{{ |
| 49 | | #include <mpi.h> |
| 50 | | #include <stdio.h> |
| 51 | | |
| 52 | | int main(int argc,char *argv[]) |
| 53 | | { |
| 54 | | int n, myid, numprocs, i=0; |
| 55 | | MPI_Status status; |
| 56 | | MPI_Init(&argc,&argv); |
| 57 | | MPI_Comm_size(MPI_COMM_WORLD,&numprocs); |
| 58 | | MPI_Comm_rank(MPI_COMM_WORLD,&myid); |
| 59 | | |
| 60 | | /* node 0 will send the first message */ |
| 61 | | if(myid==0) |
| 62 | | { |
| 63 | | n = 0; |
| 64 | | /* |
| 65 | | MPI_Send(&n, 1, MPI_INT, 1, 99, MPI_COMM_WORLD); |
| 66 | | */ |
| 67 | | printf("[Ndde %d] send number %d to Node %d\n\n", myid, n, myid+1); |
| 68 | | } |
| 69 | | |
| 70 | | /* node 1 to node n-2 will send message to the next node */ |
| 71 | | if(myid<numprocs-1) |
| 72 | | { |
| 73 | | MPI_Recv(&n, 1, MPI_INT, myid-1, 99, MPI_COMM_WORLD, &status); |
| 74 | | printf("[Node %d] recive number %d\n", myid, n); |
| 75 | | n = myid; |
| 76 | | MPI_Send(&n, 1, MPI_INT, myid+1, 99, MPI_COMM_WORLD); |
| 77 | | printf("[Ndde %d] send number %d to Node %d\n\n", myid, n, myid+1); |
| 78 | | } |
| 79 | | |
| 80 | | /* the final node n-1 will will not send any message but print itself*/ |
| 81 | | if(myid==numprocs-1) |
| 82 | | { |
| 83 | | MPI_Recv(&n, 1, MPI_INT, myid-1, 99, MPI_COMM_WORLD, &status); |
| 84 | | printf("[Node %d] recive number %d\n", myid, n); |
| 85 | | } |
| 86 | | MPI_Finalize(); |
| 87 | | return 0; |
| 88 | | } |
| 89 | | }}} |
| 90 | | [[Image(demo2-1.png)]] |
