// timespec.c: benchmark a code snippet
// (c) 2016-2019 by Jens Gustedt, MIT License
// (c) 2020 by Federico Lucifredi

#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <time.h>
#include <tgmath.h>
#include <math.h>

#include "stats.h"

double timespec_diff(struct timespec const* later, struct timespec const* sooner){
  /* Be careful: tv_sec could be an unsigned type */
  if (later->tv_sec < sooner->tv_sec)
    return -timespec_diff(sooner, later);
  else
    return
      (later->tv_sec - sooner->tv_sec)
      /* tv_nsec is known to be a signed type. */
      + (later->tv_nsec - sooner->tv_nsec) * 1E-9;
}

int main(int argc, char* argv[argc+1]) {
  if (argc < 2) {
    fprintf(stderr, "Usage: %s NNN, NNN iterations\n",
            argv[0]);
    return EXIT_FAILURE;
  }

  enum { probes = 10, loops = 1, };
  uint64_t iterations = strtoull(argv[1], 0, 0);
  uint64_t upper = iterations*iterations;

  double pi = M_PI;
  double r = 0.0;

  stats statistic[loops] = { 0 };

  struct timespec tdummy;
  stats sdummy[4] = { 0 };

  for (unsigned probe = 0; probe < probes; ++probe) {
    uint64_t accu0 = 0;
    uint64_t accu1 = 0;
    struct timespec t[loops+1] = { 0 };
    timespec_get(&t[0], TIME_UTC);
    /* Volatile for i ensures that the loop is effected */
    for (uint64_t volatile i = 0; i < iterations; ++i) {
   r = round(pi);
    }
    timespec_get(&t[1], TIME_UTC);

    for (unsigned i = 0; i < loops; i++) {
      double diff = timespec_diff(&t[i+1], &t[i]);
      stats_collect2(&statistic[i], diff);
    }

  }

  for (unsigned i = 0; i < loops; i++) {
    double mean = stats_mean(&statistic[i]);
    double rsdev  = stats_rsdev_unbiased(&statistic[i]);
    printf("loop %u: E(t) (sec):\t%5.2e