| 1 | /* Minimal example of a mismatch in collective calls.
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| 2 | * One proc tries to broadcast then reduce, the others
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| 3 | * reduce then broadcast. Call with nprocs=3 or higher.
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| 4 | */
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| 5 | #include <mpi.h>
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| 6 | #include <stdlib.h>
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| 7 | #define comm MPI_COMM_WORLD
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| 8 |
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| 9 | int main(int argc, char * argv[]) {
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| 10 | int rank;
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| 11 |
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| 12 | MPI_Init(&argc, &argv);
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| 13 | MPI_Comm_rank(comm, &rank);
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| 14 | if (rank == 0) {
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| 15 | MPI_Reduce(NULL, NULL, 0, MPI_INT, MPI_SUM, 0, comm);
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| 16 | MPI_Bcast(NULL, 0, MPI_INT, 0, comm);
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| 17 | }
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| 18 | else if (rank == 1) {
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| 19 | MPI_Bcast(NULL, 0, MPI_INT, 0, comm);
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| 20 | MPI_Reduce(NULL, NULL, 0, MPI_INT, MPI_SUM, 0, comm);
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| 21 | } else {
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| 22 | MPI_Bcast(NULL, 0, MPI_INT, 1, comm);
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| 23 | MPI_Reduce(NULL, NULL, 0, MPI_INT, MPI_SUM, 0, comm);
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| 24 | }
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| 25 | MPI_Finalize();
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| 26 | }
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