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

#define BUFSIZE 100000
#define ARRSIZE 10000000

long timespecDiff(struct timespec *timeA_p, struct timespec *timeB_p) {
   return ((timeA_p->tv_sec * 1000000000) + timeA_p->tv_nsec) -
          ((timeB_p->tv_sec * 1000000000) + timeB_p->tv_nsec);
}

int main() {

   FILE *f;
   struct timespec start, end;

   /* test standard formated writes */
   f = fopen("out1.txt","w");
   clock_gettime(CLOCK_MONOTONIC, &start);

   for (int i = 0; i < ARRSIZE; i++) {
      fprintf(f, "%.15e\n", (double)i);
   }

   clock_gettime(CLOCK_MONOTONIC, &end);
   long timeElapsed = timespecDiff(&end, &start);
   printf("Time elapsed serial: %.3f s\n", (double)timeElapsed / 1e9);
   fclose(f);

   /* parallel version */
   f = fopen("out2.txt","w");

   clock_gettime(CLOCK_MONOTONIC, &start);

#pragma omp parallel
{
   int j = 0;
   char *tmp = malloc((BUFSIZE * 22 + 1)*sizeof(char));

#pragma omp for ordered schedule(dynamic,BUFSIZE)
   for (int i = 0; i < ARRSIZE; i++) {
      sprintf(tmp + j * 22, "%.15e\n", (double)i);
      j++;
      if(j % BUFSIZE == 0) {
#pragma omp ordered
{
        fwrite(tmp, sizeof(char) * 22 * BUFSIZE, 1, f);
}
        j = 0;
      }
   }
   free(tmp);
}
   clock_gettime(CLOCK_MONOTONIC, &end);
   timeElapsed = timespecDiff(&end, &start);
   printf("Time elapsed parallel: %.3f s\n", (double)timeElapsed / 1e9);

   return 0;
}