#include <pthread.h>
#include <stdio.h>
#include <unistd.h>
#define NTHREADS 4
#define N 1000
#define MEGEXTRA 1000000
 
pthread_attr_t attr;
 
void *dowork(void *threadid)
{
  double A[N][N];
  int i,j;
  long tid;
  size_t mystacksize;

  tid = (long)threadid;
  pthread_attr_getstacksize (&attr, &mystacksize);
  printf("Thread %ld: stack size = %li bytes \n", tid, mystacksize);
  for (i=0; i<N; i++)
    for (j=0; j<N; j++)
      A[i][j] = ((i*j)/3.452) + (N-i);
  pthread_exit(NULL);
}
 
int main(int argc, char *argv[])
{
  pthread_t threads[NTHREADS];
  size_t stacksize;
  int rc;
  long t;
 
  pthread_attr_init(&attr);
  pthread_attr_getstacksize (&attr, &stacksize);
  printf("Default stack size = %li\n", stacksize);
  stacksize = sizeof(double)*N*N+MEGEXTRA;
  printf("Amount of stack needed per thread = %li\n",stacksize);
  pthread_attr_setstacksize (&attr, stacksize);
  printf("Creating threads with stack size = %li bytes\n",stacksize);
  for(t=0; t<NTHREADS; t++){
    rc = pthread_create(&threads[t], &attr, dowork, (void *)t);
    if (rc){
      printf("ERROR; return code from pthread_create() is %d\n", rc);
      return(-1);
    }
  }
  printf("Created %ld threads.\n", t);
  pthread_exit(NULL);
}