| 1 | #include "mpi.h"
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| 2 | #include "assert.h"
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| 3 |
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| 4 | int main(int argc, char *argv[]) {
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| 5 | int numtasks, rank, next, prev, buf[2], tag1=1, tag2=2;
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| 6 | MPI_Request reqs[4];
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| 7 | MPI_Status stats[4];
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| 8 |
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| 9 | MPI_Init(&argc,&argv);
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| 10 | MPI_Comm_size(MPI_COMM_WORLD, &numtasks);
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| 11 | MPI_Comm_rank(MPI_COMM_WORLD, &rank);
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| 12 |
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| 13 | prev = rank-1;
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| 14 | next = rank+1;
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| 15 | if (rank == 0) prev = numtasks - 1;
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| 16 | if (rank == (numtasks - 1)) next = 0;
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| 17 |
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| 18 | MPI_Irecv(&buf[0], 1, MPI_INT, MPI_ANY_SOURCE, MPI_ANY_TAG, MPI_COMM_WORLD, &reqs[0]);
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| 19 | MPI_Irecv(&buf[1], 1, MPI_INT, MPI_ANY_SOURCE, tag2, MPI_COMM_WORLD, &reqs[1]);
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| 20 | MPI_Isend(&rank, 1, MPI_INT, prev, tag2, MPI_COMM_WORLD, &reqs[2]);
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| 21 | MPI_Isend(&rank, 1, MPI_INT, next, tag1, MPI_COMM_WORLD, &reqs[3]);
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| 22 |
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| 23 | MPI_Waitall(4, reqs, stats);
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| 24 |
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| 25 | assert(buf[0] == prev && buf[1] == next);
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| 26 |
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| 27 | MPI_Finalize();
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| 28 | }
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