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  1. #include <stdio.h>
  2. #include <stdlib.h>
  3. #include <mpi.h>
  4.  
  5. void matrix_vector_multiply(double *A, double *b, double *c, int start_row, int end_row, int M) {
  6.     for (int i = start_row; i < end_row; i++) {
  7.         c[i] = 0;
  8.         for (int j = 0; j < M; j++) {
  9.             c[i] += A[i * M + j] * b[j];
  10.         }
  11.     }
  12. }
  13.  
  14. int parse_integer(const char *str) {
  15.     int value = 0;
  16.     while (*str) {
  17.         if (*str < '0' || *str > '9') {
  18.             return -1; // Invalid input
  19.         }
  20.         value = value * 10 + (*str - '0');
  21.         str++;
  22.     }
  23.     return value;
  24. }
  25.  
  26. int main(int argc, char **argv) {
  27.     int rank, size, N, M;
  28.  
  29.     // Initialize MPI
  30.     MPI_Init(&argc, &argv);
  31.     MPI_Comm_rank(MPI_COMM_WORLD, &rank);
  32.     MPI_Comm_size(MPI_COMM_WORLD, &size);
  33.  
  34.     // Check command-line arguments for matrix dimensions
  35.     if (argc != 3) {
  36.         if (rank == 0) {
  37.             printf("Usage: %s <num_rows> <num_columns>\n", argv[0]);
  38.         }
  39.         MPI_Abort(MPI_COMM_WORLD, EXIT_FAILURE);
  40.     }
  41.  
  42.  
  43.     // Parse matrix dimensions
  44.     N = parse_integer(argv[1]);
  45.  
  46.     M = parse_integer(argv[2]);
  47.  
  48.     if (N <= 0 || M <= 0) {
  49.         if (rank == 0) {
  50.             printf("Invalid matrix dimensions: %s x %s\n", argv[1], argv[2]);
  51.         }
  52.         MPI_Abort(MPI_COMM_WORLD, EXIT_FAILURE);
  53.     }
  54.  
  55.     double *A = NULL;
  56.     double *b = NULL;
  57.     double *c = (double *)malloc(N * sizeof(double));
  58.  
  59.     // Master process initializes the matrix and vector
  60.     if (rank == 0) {
  61.         A = (double *)malloc(N * M * sizeof(double));
  62.         b = (double *)malloc(M * sizeof(double));
  63.  
  64.         // Initialize matrix A and vector b with simple values
  65.         for (int i = 0; i < N; i++)
  66.             for (int j = 0; j < M; j++)
  67.                 A[i * M + j] = 1.0;  // Example initialization
  68.         for (int j = 0; j < M; j++)
  69.             b[j] = 1.0;  // Example initialization
  70.     }
  71.  
  72.     // Broadcast vector b to all processes
  73.     MPI_Bcast(b, M, MPI_DOUBLE, 0, MPI_COMM_WORLD);
  74.  
  75.     // Each process computes its assigned rows
  76.     int rows_per_process = N / size;
  77.     int start_row = rank * rows_per_process;
  78.     int end_row = (rank == size - 1) ? N : start_row + rows_per_process;
  79.  
  80.     double *local_c = (double *)malloc((end_row - start_row) * sizeof(double));
  81.     matrix_vector_multiply(A, b, local_c, start_row, end_row, M);
  82.  
  83.     // Gather results in the master process
  84.     MPI_Gather(local_c, end_row - start_row, MPI_DOUBLE, c, end_row - start_row, MPI_DOUBLE, 0, MPI_COMM_WORLD);
  85.  
  86.     // Master process prints the result
  87.     if (rank == 0) {
  88.         for (int i = 0; i < N; i++) {
  89.             printf("c[%d] = %f\n", i, c[i]);
  90.         }
  91.         free(A);
  92.         free(b);
  93.     }
  94.  
  95.     free(local_c);
  96.     free(c);
  97.     MPI_Finalize();
  98.     return 0;
  99.  
  100.  
  101. }
  102.  
  103.  
Success #stdin #stdout #stderr 0.23s 40676KB
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Standard input is empty
stdout
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Standard output is empty
stderr
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Error: unexpected symbol in "void matrix_vector_multiply"
Execution halted
https://ideone.com/qExNIq
language:
R (R 3.5.2)
created:
3 days ago
visibility:
public

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