test running time of 2 diff JS kernel counting

gistfile1.cpp

#include <iostream>
#include <vector>
#include <cmath>
#include <time.h>

using namespace std;

static double
JS1 (const vector<double>& a, const vector<double>& b) {
  double result = 0;
  for (size_t i = 0; i < a.size (); ++i) {
    double a_i = 0, b_i = 0;
    double ab = a[i]+b[i];
    if (a[i] != 0)
      a_i = a[i]/2 * log2(ab/a[i]);
    if (b[i] != 0)
      b_i = b[i]/2 * log2(ab/b[i]);
    result += a_i + b_i;
  }
  return result;
}

static double
JS2 (const vector<double>& a, const vector<double>& b) {
  double result = 0;
  for (size_t i = 0; i < a.size (); ++i) {
    double a_i = 0, b_i = 0;
    double ab = a[i]+b[i];
    if (a[i] != 0)
      a_i = a[i] * log2(ab/a[i]);
    if (b[i] != 0)
      b_i = b[i] * log2(ab/b[i]);
    result += 0.5*(a_i + b_i);
  }
  return result;
}

static double
diffTime (const clock_t start, const clock_t end) {

  double diffTicks = end-start;
  double inNS = (diffTicks*1e6)/CLOCKS_PER_SEC;
  return inNS;
}

static void
random_init (size_t size, vector<double>& a, vector<double>& b) {
  a.reserve (size);
  b.reserve (size);
  for (int i = 0; i < size; ++i) {
    a.push_back (rand()%100);
    b.push_back (rand()%100);
  }
}

int
main (int argc, char** argv) {
  clock_t t1, t2;
  size_t size = 1e6;
  size_t runTimes = 1e3;
  vector<double> a;
  vector<double> b;

  double diff = 0.0;
  for (int i = 0; i < runTimes; ++i) {
    a.clear (), b.clear ();
    random_init (size, a, b);
    t1 = clock ();
    JS1 (a, b);
    t2 = clock ();
    diff += diffTime (t1, t2);
  }
  cout << "JS1: " << diff << endl;

  return 0;
}