TP-openmp/BE_OpenMP_2021/butterfly/main.c

#include "aux.h"

void butterfly_seq(int n, int l, int *array);
void butterfly_par(int n, int l, int *array);

int main(int argc, char **argv)
{
  long t_start, t_end;
  int i, n, l, res;
  int *array_seq, *array_par;

  if (argc == 2)
  {
    l = atoi(argv[1]);
  }
  else
  {
    printf("Usage:\n\n ./main l\n\nwhere l defines the size of the array  n=2^l.\n");
    return 1;
  }

  n = pow(2, l);

  printf("\nGenerating an array with %d elements\n", n);
  generate_array(n, &array_seq, &res);

  array_par = (int *)malloc(n * sizeof(int));
  for (i = 0; i < n; i++)
    array_par[i] = array_seq[i];

  if (n <= 32)
  {
    printf("array_seq=[");
    for (i = 0; i < n; i++)
    {
      printf("%d ", array_seq[i]);
    }
    printf("]\n");
  }
  printf("The expected result is : %d\n\n\n\n", res);

  t_start = usecs();
  butterfly_seq(n, l, array_seq);
  t_end = usecs();

  printf("Sequential time : %8.2f msec.\n", ((double)t_end - t_start) / 1000.0);

  if (n <= 32)
  {
    printf("The result of the sequential reduction is\n");
    printf("array_seq=[");
    for (i = 0; i < n; i++)
      printf("%d ", array_seq[i]);
    printf("]\n");
  }
  printf("\n\n\n");

  t_start = usecs();
  butterfly_par(n, l, array_par);
  t_end = usecs();

  printf("Parallel   time : %8.2f msec.\n", ((double)t_end - t_start) / 1000.0);

  if (n <= 32)
  {
    printf("The result of the parallel reduction is\n");
    printf("array_par=[");
    for (i = 0; i < n; i++)
      printf("%d ", array_par[i]);
    printf("]\n\n");
  }

  check_result(n, array_par, res);
}

void butterfly_seq(int n, int l, int *array)
{

  int p, i, j, s;

  p = 0;

  while (p < l)
  {
    s = pow(2, p);
    for (i = 0; i < n; i += 2 * s)
    {
      for (j = 0; j < s; j++)
      {
        int r = operator(array[i + j], array[i + j + s]);
        array[i + j] = r;
        array[i + j + s] = r;
      }
    }
    p += 1;
  }
}

// void butterfly_par(int n, int l, int *array){

//   int p, i, j, s;

//   p = 0;

//   while(p<l){
//     s = pow(2,p);
//     for(i=0; i<n; i+=2*s){
//       #pragma omp parallel for
//       for(j=0; j<s; j++){
//         int r = operator(array[i+j],array[i+j+s]);
//         array[i+j]   = r;
//         array[i+j+s] = r;
//       }
//     }
//     p+=1;
//   }
// }

void butterfly_par(int n, int l, int *array)
{

  int p, i, j, s;

  p = 0;

#pragma omp parallel
#pragma omp single

  while (p < l)
  {
    s = pow(2, p);
    for (i = 0; i < n; i += 2 * s)
    {
      for (j = 0; j < s; j++)
#pragma omp task firstprivate(i, j, s) depend(out : array[i + j], array[i + j + s])
      {
        {
          int r = operator(array[i + j], array[i + j + s]);
          array[i + j] = r;
          array[i + j + s] = r;
        }
      }
    }
    p += 1;
  }
}