[OpenMP] Linux gyors

#include<stdio.h>
#include<stdlib.h>
#include<omp.h>

struct drand48_data puffer;
#pragma omp threadprivate( puffer )

int main(int argc, char** argv)
{
  int N;  //lovesek szama
  int kn;  // korbe talalt lovesek szama
  int i;
  double x, y;  // koord.
  double start, end;
  int seed = 0;

  switch (argc)
  {
   case 3:
    seed = atoi(argv[2]);
   case 2:
    N = atoi(argv[1]);
    break;
   default:
    printf("Hasznalat: %s N\n",argv[0]);
    return 0;
  }
  kn=0;

  start = omp_get_wtime();   // IDOMERES INDUL

  #pragma omp parallel private(i,x,y)
  {
  int mykn=0;
  int thed = omp_get_thread_num();
  srand48_r(seed+thed,&puffer);
  #pragma omp for
  for ( i = 0; i< N; i++)
    {
    drand48_r(&puffer, &x);
    drand48_r(&puffer, &y);
    if ( (x*x + y*y) <1 )
      mykn++;
    }
     #pragma omp critical
     kn +=mykn;
    }
   end = omp_get_wtime();    // IDOMERES VEGE

   printf("PI erteke = %f \n", 4.*(double)kn / N );

  printf("futasi ido: %2f\n", end-start);
   return 0;
}