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  1. #include <stdio.h>
  2. #include <stdlib.h>
  3. #include <mpi.h>
  4.  
  5. #define N 4 // Size of the matrix (Assuming square matrix for simplicity)
  6.  
  7. // Function to print matrix (for debugging)
  8. void printMatrix(double *matrix, int rows, int cols) {
  9.     for (int i = 0; i < rows; ++i) {
  10.         for (int j = 0; j < cols; ++j) {
  11.             printf("%.2f\t", matrix[i * cols + j]);
  12.         }
  13.         printf("\n");
  14.     }
  15.     printf("\n");
  16. }
  17.  
  18. // Perform Gaussian elimination using MPI
  19. void gaussianEliminationMPI(double *matrix, double *result, int rows_per_process, int my_rank, int num_procs) {
  20.     MPI_Status status;
  21.  
  22.     for (int k = 0; k < N - 1; ++k) {
  23.         // Broadcast pivot row to all processes
  24.         if (my_rank == k / rows_per_process) {
  25.             for (int proc = 0; proc < num_procs; ++proc) {
  26.                 MPI_Bcast(&matrix[k * N], N, MPI_DOUBLE, proc, MPI_COMM_WORLD);
  27.             }
  28.         }
  29.  
  30.         // Elimination
  31.         for (int i = k + 1; i < N; ++i) {
  32.             if (i / rows_per_process == my_rank) {
  33.                 double factor = matrix[i * N + k] / matrix[k * N + k];
  34.                 for (int j = k; j < N; ++j) {
  35.                     matrix[i * N + j] -= factor * matrix[k * N + j];
  36.                 }
  37.             }
  38.         }
  39.  
  40.         // Synchronize after each elimination step
  41.         MPI_Barrier(MPI_COMM_WORLD);
  42.     }
  43.  
  44.     // Back substitution (not parallelized)
  45.     if (my_rank == 0) {
  46.         for (int i = N - 1; i >= 0; --i) {
  47.             result[i] = matrix[i * N + N] / matrix[i * N + i];
  48.             for (int j = i - 1; j >= 0; --j) {
  49.                 matrix[j * N + N] -= matrix[j * N + i] * result[i];
  50.             }
  51.         }
  52.     }
  53. }
  54.  
  55. int main(int argc, char *argv[]) {
  56.     MPI_Init(&argc, &argv);
  57.  
  58.     int my_rank, num_procs;
  59.     MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);
  60.     MPI_Comm_size(MPI_COMM_WORLD, &num_procs);
  61.  
  62.     int rows_per_process = N / num_procs;
  63.     double *matrix = (double *)malloc(N * (N + 1) * sizeof(double));
  64.     double *result = (double *)malloc(N * sizeof(double));
  65.  
  66.     // Initialize matrix (for simplicity, assume a specific matrix here)
  67.     if (my_rank == 0) {
  68.         // Initialize the matrix [A | b] (assuming a specific matrix for demonstration)
  69.         matrix[0] = 2.0; matrix[1] = 1.0; matrix[2] = -1.0; matrix[3] = 8.0;
  70.         matrix[4] = -3.0; matrix[5] = -1.0; matrix[6] = 2.0; matrix[7] = -11.0;
  71.         matrix[8] = -2.0; matrix[9] = 1.0; matrix[10] = 2.0; matrix[11] = -3.0;
  72.         matrix[12] = 5.0; matrix[13] = 2.0; matrix[14] = -1.0; matrix[15] = 9.0;
  73.  
  74.         printf("Original Matrix:\n");
  75.         printMatrix(matrix, N, N + 1);
  76.     }
  77.  
  78.     // Scatter matrix to all processes
  79.     MPI_Scatter(matrix, rows_per_process * (N + 1), MPI_DOUBLE, matrix, rows_per_process * (N + 1), MPI_DOUBLE, 0, MPI_COMM_WORLD);
  80.  
  81.     // Perform Gaussian elimination
  82.     gaussianEliminationMPI(matrix, result, rows_per_process, my_rank, num_procs);
  83.  
  84.     // Gather results back to root process
  85.     MPI_Gather(result, rows_per_process, MPI_DOUBLE, result, rows_per_process, MPI_DOUBLE, 0, MPI_COMM_WORLD);
  86.  
  87.     // Print the final result (only root process)
  88.     if (my_rank == 0) {
  89.         printf("Result:\n");
  90.         for (int i = 0; i < N; ++i) {
  91.             printf("x%d = %.2f\n", i, result[i]);
  92.         }
  93.     }
  94.  
  95.     free(matrix);
  96.     free(result);
  97.  
  98.     MPI_Finalize();
  99.     return 0;
  100. }
  101.  
Success #stdin #stdout #stderr 0.28s 40716KB
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Standard output is empty
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Error: unexpected '/' in "/"
Execution halted
https://ideone.com/NBOE0o
language:
R (R 3.5.2)
created:
10 days ago
visibility:
public

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