// CSCI 2720	                Data Structures			     Spring 2004

// timedemo.cc
// demonstration of timing function 

#include <iostream>
using namespace std;
    
int main( ) {

  int i, j, flag, count, MAX = 50000;
  clock_t clock1, clock2;  // declare variables to store times, in clock ticks 
  clock1 = clock( );  // call just before code segment to time

  count = 0;
  for (i = 2; i <= MAX; i++) {
    flag = 1;
    for (j = 2; j*j <= i; j++) {
      if (i % j == 0) { 
	flag = 0;
	break;
      }
    }
    count += flag;
  }; //for loop over i 

  clock2 = clock( ); // call just after code segment to time
  cout << "starting time: " << clock1 << " in ticks.\n";
  cout << "finish time:   " << clock2 << endl;
  cout << "net CPU Time = " << (clock2 - clock1)/(CLOCKS_PER_SEC/1.0e3);
  cout << " milliseconds.\n\n";

  cout << "no. primes =< " << MAX << " is: " << count << '\n' << endl;

  cout << "The next run should be slower, but give the same result.\n" << endl;

  clock1 = clock( ); // record start time, as in 1st run

  count = 0;
  for (i = 2; i <= MAX; i++) {
    flag = 1;
    for (j = 2; j*j <= i; j++) {
      if (i % j == 0)  
	flag = 0;
    }
    count += flag;
  }; //for loop over i 

  clock2 = clock( ); // record finish time, as in 1st run 
  cout << "second starting time: " << clock1 << " in ticks.\n";
  cout << "second finish time:   " << clock2 << endl;
  cout << "second net CPU Time = " << (clock2 - clock1)/(CLOCKS_PER_SEC/1.0e3);
  cout << " milliseconds.\n\n";

  cout << "no. primes =< " << MAX << " is: " << count << '\n' << endl;

  return 0;
}