120 lines
2.6 KiB
C
120 lines
2.6 KiB
C
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#include <stdio.h>
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#include <stdlib.h>
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#include <mpi.h>
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void multAv(double x[], double *A, double y[], int m, int n);
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void init0(double x[], int n);
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int main(int argc, char *argv[])
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{
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int size;
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int const n = 12;
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int my_rank;
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MPI_Init(&argc, &argv);
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// Get number of processes and check that 4 processes are used
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MPI_Comm_size(MPI_COMM_WORLD, &size);
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if (size != 4)
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{
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printf("This application is meant to be run with 4 MPI processes.\n");
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MPI_Abort(MPI_COMM_WORLD, EXIT_FAILURE);
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}
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// Get my rank
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MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);
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// Declaration and Initialization of A (one for all components)
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// the number of bloc of lines, b, is the same for all node
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// (if you don't change the constants)
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int b = n / size;
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double *A;
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A = (double *)malloc(b * n * sizeof(double));
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for (int i = 0; i < b; i++)
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{
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for (int j = 0; j < n; j++)
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{
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A[i * n + j] = 1.0;
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// A[i*n + j] = (double) my_rank;
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// A[i*n + j] = (double) my_rank*(i+1)+(j+1);
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// printf("Process [%d], A[%d][%d] = %f\n", my_rank, i, j, A[i*n+j]);
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}
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}
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// reference vector to verify that the global vector is correct
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double v_ref[n];
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for (int i = 0; i < n; i++)
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{
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v_ref[i] = (double)i;
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}
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// local vector
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double v_local[b];
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for (int i = 0; i < b; i++)
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{
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v_local[i] = (double)b * my_rank + i;
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// printf("Process [%d], v_local[%d] = %f\n", my_rank, i, v_local[i]);
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}
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// global vector
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double v_global[n];
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init0(v_global, n);
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// Use a collective communication in order to gather on ALL the nodes the
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// part of the local vector into the global vector
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MPI_Allgather(v_local, b, MPI_DOUBLE, v_global, b, MPI_DOUBLE, MPI_COMM_WORLD);
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// the node 2 checks if the global vector is correct
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if (my_rank == 2)
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{
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for (int i = 0; i < n; i++)
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{
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printf("Process [%d], vérif[%d] = %f\n", my_rank, i, v_global[i] - v_ref[i]);
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}
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}
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MPI_Barrier(MPI_COMM_WORLD);
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// vector x_loc = A * v_global
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double x_loc[b];
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init0(x_loc, b);
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// Perform the multiplication
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multAv(x_loc, A, v_global, b, n);
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// each node displays x (with A, full of ones, all the components of x should be the same)
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for (int i = 0; i < b; i++)
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{
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printf("Process [%d], x_loc[%d] = %f\n", my_rank, i, x_loc[i]);
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}
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MPI_Finalize();
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return EXIT_SUCCESS;
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}
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void multAv(double x[], double *A, double y[], int m, int n)
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{
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for (int i = 0; i < m; i++)
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{
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x[i] = 0.0;
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for (int j = 0; j < n; j++)
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{
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x[i] += A[i * n + j] * y[j];
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}
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}
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return;
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}
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void init0(double x[], int n)
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{
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for (int i = 0; i < n; i++)
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{
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x[i] = 0.0;
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}
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return;
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}
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