| 1 | /**
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| 2 | * This program illustrates MPI_Alltoallv.
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| 3 | * online source: http://mpi.deino.net/mpi_functions/MPI_Alltoallv.html
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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 | #include <stdio.h>
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| 8 | /*
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| 9 | This program tests MPI_Alltoallv by having processor i send different
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| 10 | amounts of data to each processor.
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| 11 | The first test sends i items to processor i from all processors.
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| 12 | */
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| 13 | int main( int argc, char **argv )
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| 14 | {
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| 15 | MPI_Comm comm;
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| 16 | int *sbuf, *rbuf;
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| 17 | int rank, size;
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| 18 | int *sendcounts, *recvcounts, *rdispls, *sdispls;
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| 19 | int i, j, *p, err;
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| 20 |
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| 21 | MPI_Init( &argc, &argv );
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| 22 | err = 0;
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| 23 | comm = MPI_COMM_WORLD;
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| 24 | /* Create the buffer */
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| 25 | MPI_Comm_size( comm, &size );
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| 26 | MPI_Comm_rank( comm, &rank );
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| 27 | sbuf = (int *)malloc( size * size * sizeof(int) );
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| 28 | rbuf = (int *)malloc( size * size * sizeof(int) );
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| 29 | if (!sbuf || !rbuf) {
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| 30 | fprintf( stderr, "Could not allocated buffers!\n" );
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| 31 | MPI_Abort( comm, 1 );
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| 32 | }
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| 33 | /* Load up the buffers */
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| 34 | for (i=0; i<size*size; i++) {
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| 35 | sbuf[i] = i + 100*rank;
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| 36 | rbuf[i] = -i;
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| 37 | }
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| 38 | /* Create and load the arguments to alltoallv */
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| 39 | sendcounts = (int *)malloc( size * sizeof(int) );
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| 40 | recvcounts = (int *)malloc( size * sizeof(int) );
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| 41 | rdispls = (int *)malloc( size * sizeof(int) );
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| 42 | sdispls = (int *)malloc( size * sizeof(int) );
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| 43 | if (!sendcounts || !recvcounts || !rdispls || !sdispls) {
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| 44 | fprintf( stderr, "Could not allocate arg items!\n" );fflush(stderr);
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| 45 | MPI_Abort( comm, 1 );
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| 46 | }
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| 47 | for (i=0; i<size; i++) {
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| 48 | sendcounts[i] = i;
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| 49 | recvcounts[i] = rank;
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| 50 | rdispls[i] = i * rank;
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| 51 | sdispls[i] = (i * (i+1))/2;
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| 52 | }
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| 53 | MPI_Alltoallv( sbuf, sendcounts, sdispls, MPI_INT,
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| 54 | rbuf, recvcounts, rdispls, MPI_INT, comm );
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| 55 | /* Check rbuf */
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| 56 | for (i=0; i<size; i++) {
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| 57 | p = rbuf + rdispls[i];
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| 58 | for (j=0; j<rank; j++) {
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| 59 | if (p[j] != i * 100 + (rank*(rank+1))/2 + j) {
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| 60 | fprintf( stderr, "[%d] got %d expected %d for %dth\n",
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| 61 | rank, p[j],(i*(i+1))/2 + j, j );
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| 62 | fflush(stderr);
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| 63 | err++;
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| 64 | }
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| 65 | }
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| 66 | }
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| 67 | free( sdispls );
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| 68 | free( rdispls );
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| 69 | free( recvcounts );
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| 70 | free( sendcounts );
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| 71 | free( rbuf );
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| 72 | free( sbuf );
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| 73 | MPI_Finalize();
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| 74 | return 0;
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| 75 | }
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