并行计算之向量的计算-蒲公英云

并行计算之向量的计算

#include <stdio.h>
#include <stdlib.h>
#include <mpi.h>
void Read_n(int* n_p, int* local_n_p, int my_rank,
int comm_sz, MPI_Comm comm);
void Allocate_vectors(double** local_x_pp, 
  double** local_y_pp,
  double** local_z_pp, 
  int local_n, MPI_Comm comm);
void Read_vector(double local_a[], int local_n, 
 int n, char vec_name[], 
 int my_rank, MPI_Comm comm);
void Print_vector(double local_b[], int local_n,
  int n, char title[], 
  int my_rank, MPI_Comm comm);
void Parallel_vector_sum(double local_x[], 
 double local_y[], 
 double local_z[], 
 int local_n);
int main(void) {
   int n, local_n;
   int comm_sz, my_rank;
   double *local_x, *local_y, *local_z;
   MPI_Comm comm;
   MPI_Init(NULL, NULL);
   comm = MPI_COMM_WORLD;
   MPI_Comm_size(comm, &comm_sz);
   MPI_Comm_rank(comm, &my_rank);
   Read_n(&n, &local_n, my_rank, comm_sz, comm);
   printf("Proc %d > n = %d, local_n = %d\n", 
      my_rank, n, local_n);
   Allocate_vectors(&local_x, &local_y, 
                &local_z, local_n, comm);
   Read_vector(local_x, local_n, n, "x", my_rank, comm);
   Print_vector(local_x, local_n, n, "x is", my_rank, comm);
   Read_vector(local_y, local_n, n, "y", my_rank, comm);
   Print_vector(local_y, local_n, n, "y is", my_rank, comm);
   Parallel_vector_sum(local_x, local_y, local_z, local_n);
   Print_vector(local_z, local_n, n, "The sum is", 
            my_rank, comm);
   free(local_x);
   free(local_y);
   free(local_z);
   MPI_Finalize();
   return 0;
}
void Read_n(int* n_p, int* local_n_p, int my_rank,
int comm_sz, MPI_Comm comm) {
   if (my_rank == 0) {
      printf("What's the order of the vectors?\n");
      scanf("%d", n_p);
   }
   MPI_Bcast(n_p, 1, MPI_INT, 0, comm);
   *local_n_p = *n_p/comm_sz;
}
void Allocate_vectors(double** local_x_pp, 
  double** local_y_pp,
  double** local_z_pp, 
  int local_n, MPI_Comm comm) {
   *local_x_pp = (double *)malloc(local_n*sizeof(double));
   *local_y_pp = (double *)malloc(local_n*sizeof(double));
   *local_z_pp = (double *)malloc(local_n*sizeof(double));
}
void Read_vector(double local_a[], int local_n, 
 int n, char vec_name[], 
 int my_rank, MPI_Comm comm) {
   double* a = NULL;
   int i;
   if (my_rank == 0) {
      a = (double *)malloc(n*sizeof(double));
      printf("Enter the vector %s\n", vec_name);
      for (i = 0; i < n; i++)
         scanf("%lf", &a[i]);
      MPI_Scatter(a, local_n, MPI_DOUBLE, 
  local_a, local_n, MPI_DOUBLE, 0, comm);
      free(a);
   }
   else {
      MPI_Scatter(a, local_n, MPI_DOUBLE, 
  local_a, local_n, MPI_DOUBLE, 0, comm);   
   }
}
void Print_vector(double local_b[], int local_n,
  int n, char title[], 
  int my_rank, MPI_Comm comm) {
   double* b = NULL;
   int i;
   if (my_rank == 0) {
      b = (double *)malloc(n*sizeof(double));
      MPI_Gather(local_b, local_n, MPI_DOUBLE, b, 
  local_n, MPI_DOUBLE, 0, comm);
      printf("%s\n", title);
      for (i = 0; i < n; i++)
         printf("%f ", b[i]);
      printf("\n");
      free(b);
   } 
   else {
      MPI_Gather(local_b, local_n, MPI_DOUBLE, b, 
  local_n, MPI_DOUBLE, 0, comm);  
   }
}
void Parallel_vector_sum(double local_x[], 
 double local_y[], 
 double local_z[], 
 int local_n) {
   int local_i;
   for (local_i = 0; local_i < local_n; local_i++)
      local_z[local_i] = local_x[local_i] + local_y[local_i];
}