Multithread

#include <windows.h>
#include <math.h>
#include <stdlib.h>
#include <stdio.h>
#include <time.h>

#define NTHRD 1   // broj niti
#define N 10000

float a[N];
long grp[NTHRD];  // granica početak
long grk[NTHRD];  // granica kraj
HANDLE hn[NTHRD]; // HANDLE-ovi niti
long ids[NTHRD];  // ID-ovi od niti (kreću od 0,1,2,3,...)
float sp[NTHRD];  // parcijalne sume
volatile float sm;

DWORD WINAPI nit( VOID *p )
{
  int i, j; float s2;
  int *id = (int *)p;
  printf( "I am thread %d\n", *id );
  for (i=grp[*id]; i<grk[*id]; i++)
  {
      s2 = 0;
      for (j=0; j<N; j++) s2 = s2 + sqrt( a[j] );
      sp[*id] = sp[*id] + a[i]/s2;
  }
  return 0;
}

int main(int argc, char *argv[])
{
  int i,j;
  float s, s2;
  clock_t t1, t2;
  for (i=0; i<N; i++){
       srand ( time(NULL) );
      a[i] = rand();
}

  t1 = clock();
  s = 0;
  for (i=0; i<N; i++)
  {
      s2 = 0;
      for (j=0; j<N; j++) s2 = s2 + sqrt( a[j] );
      s = s + a[i]/s2;
  }
  t2 = clock();

  printf( "%.3f\n", s );
  printf( "Time: %dms\n", t2-t1 );

  t1 = clock();
  long delta = N/NTHRD;
  for (i=0; i<NTHRD; i++)
  {
      grp[i] = delta*i;
      grk[i] = delta*(i+1);
      ids[i] = i;
      hn[i] = CreateThread( NULL, 0, nit, &ids[i], 0, NULL );
  }
  WaitForMultipleObjects( NTHRD, hn, TRUE, INFINITE );
  s = 0;
  for (i=0; i<NTHRD; i++) s = s + sp[i];
  t2 = clock();
  printf( "%.3f\n", s );
  printf( "Time for %d thread's: %dms\n", NTHRD, t2-t1 );
  system("PAUSE");
  return EXIT_SUCCESS;
}