measuring execution time for C++ program

[jainyi]

Hi,
I want to calculate execution time for a program computing fibonacci number in C++. I have programmed two functions (one using recursion and other using divide and conquer huristic) to compute fibonnaci number for (n=4,8,16,32,64). Now i want to compare these two methods. Though i have used following method to compute execution time but it is not precise as yielding 0 ticker time for n=4,8,16 in both the cases

double execClock(clock_t c1,clock_t c2)
        {
            double t=clock1-clock2;
            double tim=(t*10)/CLOCKS_PER_SEC;
            return tim;
        }
 

Is there anyother method which is more accurate for lower values of n, i am working in Inet/Windows XP/Dev C++ environment?

While following using recursive method

    int fib(int n)
         {
            if (n <= 1)
               return n;
            else
               return fib(n-1) + fib (n-2);
         }
 

i can not compute fibonacci number for n=64, just system gets hanged, CPU usage reaches to 97% for the application, it seems it has struk in the computation

With Regards
Jianyi

[Savage]

Hi,
I want to calculate execution time for a program computing fibonacci number in C++. I have programmed two functions (one using recursion and other using divide and conquer huristic) to compute fibonnaci number for (n=4,8,16,32,64). Now i want to compare these two methods. Though i have used following method to compute execution time but it is not precise as yielding 0 ticker time for n=4,8,16 in both the cases

double execClock(clock_t c1,clock_t c2)
        {
            double t=clock1-clock2;
            double tim=(t*10)/CLOCKS_PER_SEC;
            return tim;
        }
 

Is there anyother method which is more accurate for lower values of n, i am working in Inet/Windows XP/Dev C++ environment?

While following using recursive method

    int fib(int n)
         {
            if (n <= 1)
               return n;
            else
               return fib(n-1) + fib (n-2);
         }
 

i can not compute fibonacci number for n=64, just system gets hanged, CPU usage reaches to 97% for the application, it seems it has struk in the computation

With Regards
Jianyi

The most precise method i know is QueryPerformanceCounter and QueryPerformanceFrequency which are defined in windows.h.

You use it like:

LARGE_INTEGER lFreq;
LARGE_INTEGER lTime1;
LARGE_INTEGER lTime2;
long diffTicks;
float diffSecs;
 
QueryPerformanceCounter(&lFreq);
QueryPerformanceFrequency(&lTime1);
//function
QueryPerformanceFrequency.(&lTime2);
diffTicks=lTime1.QuadPart-lTime2.QuadPart;//ticks passed
diifSecs=(diffTicks/lFreq.QuadPart);//secs passed.

Savage

[jainyi]

Thanks for reply

but it is producing no result; 0 ticks and 0 seconds for each n i.e. 4,8,16, 32

  while (quit != 'x')
            {
                LARGE_INTEGER lFreq;
                LARGE_INTEGER lTime1;
                LARGE_INTEGER lTime2; 
                long diffTicks;
                float diffSecs;
                int i;
                for(i=4;i<=66;i=i*2)
                  {
                   QueryPerformanceCounter(&lFreq);
                   QueryPerformanceFrequency(&lTime1);
                   cout<<fib(i);
                   QueryPerformanceFrequency(&lTime2);
                   diffTicks=lTime1.QuadPart-lTime2.QuadPart;//ticks passed
                   diffSecs=(diffTicks/lFreq.QuadPart);//secs passed.
                   cout<<" With ticks: " <<diffTicks<<" and seconds: "<<diffSecs<<endl;
                  }       
                cout << endl << " Press x to quit "<<endl;
                cin >> quit;
            };
 
===========================================
 int fib(int n)
         {
            if (n <= 1)
               return n;
            else
               return fib(n-1) + fib (n-2);
         }
 

Output is zero ticks and zero seconds for each computed number

Jianyi

[Savage]

My bad,wher you have QueryPerformanceFrequency put QueryPerformanceCounter and vise versa.Also subtract time2 from time 1 not vise versa.

Savage

[jainyi]

Though i have got time2 - time1 but notgetting about function calls. Do you mean this way

                   QueryPerformanceFrequency(&lTime1);
                   QueryPerformanceCounter(&lFreq);
                   cout<<fib(i);
                   QueryPerformanceFrequency(&lTime2);
                   diffTicks=lTime2.QuadPart-lTime1.QuadPart;//ticks passed
                   diffSecs=(diffTicks/lFreq.QuadPart);//secs passed.
 

Jianyi

[Savage]

Though i have got time2 - time1 but notgetting about function calls. Do you mean this way

                   QueryPerformanceFrequency(&lTime1);
                   QueryPerformanceCounter(&lFreq);
                   cout<<fib(i);
                   QueryPerformanceFrequency(&lTime2);
                   diffTicks=lTime2.QuadPart-lTime1.QuadPart;//ticks passed
                   diffSecs=(diffTicks/lFreq.QuadPart);//secs passed.
 

Jianyi

No,like this:

QueryPerformanceFrequency(&lFreq);
QueryPerformanceCounter(&lTime1);
//function
QueryPerformanceCounter(&lTime2);
.
.
.
.

[jainyi]

Thank you

Now it is fine

Jianyi