math_benchmark.cpp

#include "hsTimer.h"
#include <stdlib.h>
#include <iostream>
#include <tchar.h>
#include <math.h>

using namespace std;
using namespace MobyDisk;

class LinearCongruentRnd {

private:
   __int64 state;

public:
   LinearCongruentRnd(int start) {
      state = start;
   }

   unsigned int nextInt()
   {
      state = state*7919 + 104729;
      return static_cast<unsigned int>(state & 0xFFFFFFFF);
   }

   double nextDouble() {
      return (double)nextInt()/UINT_MAX;
   }
};

void calculatePI()
{
   double pi = 0;                      // Accumulated value of pi
   double ms = 0;                      // Elapsed time
   int count = 0;                      // Number of iterations run
   static const int testTimeMS = 10000;      // Run the test for 10 seconds

   LinearCongruentRnd rand(12345);

   hsTimer::init();
   hsTime start = hsTimer::getTime();
   do
   {
      // Random sampling method similar to the buffon needle experiment
      double x,y;    // Random coordinates -0.5...0.5
      int inside=0;  // Number of hits inside the circle
      int outside=0; // Number of hits outside the circle

      // Run a bunch of samples
      for (int samples=0; samples<10000000; samples++)
      {
         // Generate coordinates
         x = rand.nextDouble() - 0.5;
         y = rand.nextDouble() - 0.5;

         // Inside the circle?
         if (x*x+y*y<0.25)
            inside++;
         else
            outside++;
      }

      // Calculate the value of pi
      double new_pi = 4*static_cast<double>(inside)/(inside+outside);

      // Accumulate it
      pi += new_pi;
      count++;

      // How long did this take?
      ms = hsTimer::getElapsed(start);
   } while (ms < testTimeMS);

   // PI is
   cout << "PI = " << pi/count << endl;
   cout << "Iterations ran = " << count << endl;
   cout << "Time = " << ms << " ms" << endl;
   cout << "Iterations per second = " << 1000*count/ms << endl;
}


int _tmain(int argc, _TCHAR* argv[])
{

   calculatePI();

   return 0;
}