#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <math.h>
#include <mach/mach_time.h>

//Raw mach_absolute_times going in, difference in seconds out
double subtractTimes( uint64_t endTime, uint64_t startTime )
{
    uint64_t difference = endTime - startTime;
    static double conversion = 0.0;
    
    if( conversion == 0.0 )
    {
        mach_timebase_info_data_t info;
        kern_return_t err = mach_timebase_info( &info );
        
		//Convert the timebase into seconds
        if( err == 0  )
			conversion = 1e-9 * (double) info.numer / (double) info.denom;
    }
    
    return conversion * (double) difference;
}

int main() {
    
    int i, j, count;
    
    uint64_t start,stop;
    
	double current = 0.0;
	double answer = 0.0;
	double elapsed = 0.0;
	
	int dim1 = 256;
	int dim2 = 256;
	int size = 4*dim1*dim2;
	
	//Allocate some memory and warm it up
    double *array = (double*)malloc(size*sizeof(double));
	for(i=0;i<size;i++) array[i] = (double)i;
	
	count = 5;
	for(i=0;i<count;i++){
		
		//Get the starting mach time
		start = mach_absolute_time();
		
		//do some work
		for(j=0;j<size;j++){
			answer += sqrt(array[j]);
		}
		
		//Get the final mach time
		stop = mach_absolute_time();
		
		//Determine the time in seconds
		current = subtractTimes(stop,start);
		printf("Time for iteration: %1.12lf for answer: %1.12lf\n",current, answer);
		
		//Add it to the total counter (for getting the average, see below)
		elapsed += current;
	}    
    
    printf("\nAverage time in seconds = %1.12lf for answer: %1.12lf\n",elapsed/count,answer);
    
	free(array);
	
    return 0;
}