source: CIVL/examples/openMP/dotProduct_critical.cvl@ 82c2f5c

// dot product implementation with critical region.

/*
   OpenMP example program which computes the dot product of two arrays a and b
   (that is sum(a[i]*b[i]) ) using explicit synchronization with a critical region.
   Compile with gcc -O3 -fopenmp omp_critical.c -o omp_critical
*/
// Online source: http://users.abo.fi/mats/PP2012/examples/OpenMP/omp_critical.c

#include <civlc.h>
#include <stdio.h>
#include <stdlib.h>
#include "omp.cvh"
$input int N;

int main (int argc, char *argv[]) {
  
  double a[N], b[N];
  double localsum, sum = 0.0;
  int i, tid, nthreads;
 
  /* helper variables shared by all threads*/
  _Bool __critical_0 = $false; //default crticial region variable name
  
  /* parallel procedure */
  void __parallel_0(int __tid) {
        #include "omp_thread.cvh"
    double i, localsum; //private(i, localsum)
    
        tid = omp_get_thread_num();
        
        if(tid == 0) { //#pragma omp master
                nthreads = omp_get_num_threads();
            printf("Number of threads = %d\n", nthreads);
        }
        
        /* The procedure of each thread for the first for loop */
        void __for_0(int __tid, int __start, int __end, int __extra){
          for(int __i = __start; __i < __end; __i++) {
            a[__i] = b[__i] = (double)__i;
          }
          if(__extra > 0) {
            a[__extra] = b[__extra] = (double)__extra;
          }
        }
        
        {//#pragma omp for
         //  for (i=0; i < N; i++)
         //    localsum = localsum + (a[i] * b[i]);
          int __start = __for_start(__tid, N);
          int __end = __for_end(__tid, N);
          int __extra = __for_extra(__tid, N);
        
          __for_0(__tid, __start, __end, __extra);
        }

        localsum = 0.0;
        
        /* The procedure of each thread for the second for loop */
        void __for_1(int __tid, int __start, int __end, int __extra){
      for(int __i = __start; __i < __end; __i++) {
            localsum = localsum + (a[__i] * b[__i]);
          }
          if(__extra > 0) {
            localsum = localsum + (a[__extra] * b[__extra]);
          }
        }
        
        {//#pragma omp for
     //  for (i=0; i < N; i++)
     //    localsum = localsum + (a[i] * b[i]);
          int __start = __for_start(__tid, N);
          int __end = __for_end(__tid, N);
          int __extra = __for_extra(__tid, N);
                
          __for_1(__tid, __start, __end, __extra);
    }
        
        {//#pragma omp critical
          $when(!__critical_0) __critical_0 = $true;
          sum = sum+localsum;
          __critical_0 = $false;
        }
  }
  
  $proc __parallel_0_procs[OMP_NUM_THREADS];
  
  /* Create processes to conduct the parallel region  */
  for(i = 0; i < OMP_NUM_THREADS; i++) {        
          __parallel_0_procs[i] = $spawn __parallel_0(i);
  }
  for(i = 0; i < OMP_NUM_THREADS; i++) {        
          $wait(__parallel_0_procs[i]);
  }
  printf("   Sum = %f\n",sum);
}