// ----------------------------------------------------------------------------
// clockTest.cpp
// Written by:
// Last Modified:
//
// Program with two timing examples
// 1. frequency of primes
// 2. looping calling exponential function
//
// ----------------------------------------------------------------------------
#include <ctime>       // clock_t, clock, CLOCKS_PER_SEC
#include <cmath>       // sqrt
#include <iostream>    // cout

// ----------------------------------------------------------------------------
// Prototypes - global function declarations
// ----------------------------------------------------------------------------
clock_t freqySetup(long n);
int    frequencyOfPrimes(long n);
clock_t LoopingTime(long numIterations);

using namespace std;

struct DataPoints
{
	clock_t time;
	long    n;
};

// ----------------------------------------------------------------------------
// main - it all begins here
// ----------------------------------------------------------------------------
int main ()
{
	cout << "This is a timing test program.\n";
	cout << "The numbers used here are _small_ so time variations will be _tiny_\n";
	cout << "The lesson is to see that runtimes do indeed vary.\n";
	cout << "Run this program 5 times and you may notice the variations.\n";
	cout << "Compare to same program running on different machine may be more useful.\n";
	cout << "Or on same machine but with more programs running in the background.\n";
	cout << endl;
	
	long k = 1;
	DataPoints freqyData[10000];  // pick big array size... just in case we really want a lot of data
	DataPoints loopyData[10000];
	int fIdx = 0;
	int lIdx = 0;
	
    // init all data	
	for (int y = 0; y < 10000; y++)
	{
		freqyData[y].time = 0;
		freqyData[y].n    = -1;
		loopyData[y].time = 0;
		loopyData[y].n    = -1;
	}
	
//    for (long i = 100000; i <= 25000000; i+=300000)  // use for larger data set
    for (long i = 10000; i <= 3000000; i+=300000)
	{
		freqyData[fIdx].n    = i;
		freqyData[fIdx].time = freqySetup(i);
		++fIdx;
		
		++k;
		if (k % 3 == 0)
		{
           loopyData[lIdx].n    = 2*i;
           loopyData[lIdx].time = LoopingTime(2*i);
           ++lIdx;
           
           k = 1;
	   }
	}

    cout << "\n======================================================================\n\n";
    // Print out summary data
	cout << "Freqy Data\n";
    for (long g = 0; g < fIdx; g++)
    {
        cout << "n = " << freqyData[g].n << " time = \t" << freqyData[g].time << " clicks, ";
        cout << (freqyData[g].time / (double)CLOCKS_PER_SEC) << " seconds\n";
    }
	
	cout << "Loopy Data\n";
    for (long h = 0; h < lIdx; h++)
    {
        cout << "n = " << loopyData[h].n << " time = \t" << loopyData[h].time << " clicks, ";
        cout << (loopyData[h].time / (double)CLOCKS_PER_SEC) << " seconds\n";
    }
	
    return 0;
}

// ----------------------------------------------------------------------------
// freqySetup
// This function is used just to put a timing wrapper around
// calling frequencyOfPrimes
// Returns the click difference endTime - startTime
// ----------------------------------------------------------------------------
clock_t freqySetup(long n)
{
    clock_t t;
    int f;
    t = clock();
  
    cout <<"Frequency of Primes, n = " << n << endl;
    f = frequencyOfPrimes(n);
    cout << "The number of primes <= " << n << " is: " << f << endl;
    t = clock() - t;
    cout << "     Time = " << t << " clicks = " <<  (t / (double)CLOCKS_PER_SEC) << " seconds\n";
    
    return t;
}

// ----------------------------------------------------------------------------
// frequency of primes
// Counts the number of primes less than n, returns the result
// Expect n > 0, if not use -n, return -1 if zero sent
// ----------------------------------------------------------------------------
int frequencyOfPrimes (long n) 
{
    if (n < 0) 
    {  
		n = -n;   
	}
    
    long q = 0;
    long i,j;
    int  freq = n-1;
    for (i=2; i<=n; ++i) 
    {
	    for (j=sqrt(i); j>1; --j) 
	    {
		    if (i % j==0) 
		    {
			    --freq; 
			    break;   // hack to exit the inner for-loop early
			              // a good programmer would re-write the loop logic
			              // not use a cheap hack   =)
		    }
	    }
	    ++q;
        if (q % 50000 == 0)
        {
			cout << ".";
			q = 0;
		}
    }
    cout << endl;
    
    return freq;
}

// ----------------------------------------------------------------------------
// LoopingTime
// numIterations = maximum number value to loop to
// exp(i) will be called each iteration of the for-loop
// ----------------------------------------------------------------------------
clock_t LoopingTime(long numIterations)
{
    cout << "\nFor-loop exp test... n = " << numIterations << endl;
    clock_t start = clock();
    for (long i = 0; i < numIterations; ++i)
    {
        exp(log((double)i));
        if (i % 500000 == 0)
        {
			cout << "++";
		}
    }
    cout << endl;
    clock_t finish = clock();
    clock_t t      = finish - start;
    
    cout << "     Time = " << t << " clicks =";
    cout << ( t / (double)CLOCKS_PER_SEC) << " seconds.\n";
    
    return t;
 }   

// ----------------------------------------------------------------------------
// ----------------------------------------------------------------------------
// end of file