/* 
  
   Write  to an array in parallel. 


*/ 


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



int main(int argc, char** argv) {

  int num_threads;  //nb threads requested by user
  long n;  //size of array 
  int block; 

  double t1, t2; 

  //read args from user 
  if (argc != 4)  {
    printf("usage:  %s [n] [nthreads] [k]\n", argv[0]); 
    exit(1); 
  } 
  n = atol(argv[1]); 
  num_threads = atoi(argv[2]); 
  block = atoi(argv[3]); 
  printf("using n=%ld, numthreads=%d block ==%d\n", n, num_threads, block); 
  
  //allocate visibility array 
  int* vis = (int*) malloc(n * sizeof(int)); 
  assert(vis); 

  t1 = omp_get_wtime(); 
  
  long i; 
  double sum = 0; 
  omp_set_num_threads(num_threads); 
#pragma omp parallel  
  { 
    //private variables to each thread  
    double localsum = 0; 

    int thread_id = omp_get_thread_num(); 
    if (thread_id == 0) {
      printf("[master] nb. threads is  %d\n", omp_get_num_threads());
    }

    //printf("Start(%d)\n", thread_id); 
    
#pragma omp for schedule(static, block) 
    for (i=0; i<n; i++) {
      vis[i] = i;
      //localsum += vis[i]; 
      //localsum += i; 
    }
    
    // printf("Done(%d)\n", thread_id); 
 
  
    //#pragma omp critical 
    //sum += localsum; 
    
  } //omp parallel 
  
  t2 = omp_get_wtime();   
  
  //  if (sum != n *(n-1)/2) {
  //printf("write error\n");
  //exit(1); 
  //}
  printf("Done.  time = %.3f milliseconds\n", (t2-t1)*1000);
  free(vis); 
  return 0; 
}