How to calculate time execution and cpu speding for a function in C++

Question

I have finished writing a function and I want to compare time and cpu execution of the function with other function. This is code to calculate time execution but I not sure it accuracy. Do you have accuracy code to calculate time and cpu spending for one function in C++?

//Only time execution. CPU spending? #include "stdafx.h" #include <iostream> #include <time.h> using namespace std; int _tmain(int argc, _TCHAR* argv[]) { clock_t start, end; start = clock(); for(int i=0;i<65536;i++) cout<<i<<endl; end = clock(); cout << "Time required for execution: " << (double)(end-start)/CLOCKS_PER_SEC << " seconds." << "\n\n"; return 0; }

possible duplicate of How to know calculate the execution time of an algorithm in c++? — Mat
– Mat, Commented May 22, 2013 at 7:46
Since you tagged this Visual-C++, have you tried the Visual Profiler ? (Not available in every version though). — JBL
– JBL, Commented May 22, 2013 at 7:48
possible duplicate of How to Calculate Execution Time of a Code Snippet in C++ — Roger Rowland
– Roger Rowland, Commented May 23, 2013 at 5:01

syam · Accepted Answer · 2013-05-22 07:58:33Z

6

In C++11 you should use std::chrono::high_resolution_clock which under the hood uses the clock source with the smallest tick period provided by the system:

#include <chrono> auto start = std::chrono::high_resolution_clock::now(); //... auto end = std::chrono::high_resolution_clock::now(); auto elapsed = std::chrono::duration_cast<std::chrono::milliseconds>(end - start);

edited May 22, 2013 at 7:58

answered May 22, 2013 at 7:49

syam

15.1k3 gold badges46 silver badges68 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

user2408476 Over a year ago

Sorry. I am using visual studio C++ 2010 . What is library that your code need include ?

syam Over a year ago

@user2408476: I'm afraid I don't know how well Visual Studio supports C++11 features. If including <chrono> doesn't work, you may want either to use boost which provides a high_resolution_clock implementation, or Mats Petersson's QueryPerformanceCounter solution.

SChepurin Over a year ago

<chrono> is not supported in VC++2010. For high precision time measurements you should use QueryPerformanceCounter.

BlueTrin Over a year ago

Is this the CPU time or computer time ?

Mats Petersson · Accepted Answer · 2013-05-22 07:48:47Z

For this particular code, I'm pretty sure your code is quite OK.

For short periods, you may need to use more precise timing functions, such as Windows' QueryPerformanceCounter and QueryPerformanceFrequency to get higher precision timing.

user2088790 · Accepted Answer · 2013-05-22 07:59:37Z

The easiest way I know of to get precise time estimates is to use an OpenMP function:

#include <stdio.h> #include <omp.h> int main() { double dtime = omp_get_wtime(); foo(); dtime = omp_get_wtime() - dtime; printf("time in seconds %f\n", dtime); }

In gcc compile with -fopenmp. In visual studio turn on OpenMP support under C++/Language Support. BTW, OpenMP now works in Visual Studio 2012 express. For CPU time profiling you can try http://developer.amd.com/tools-and-sdks/heterogeneous-computing/amd-codeanalyst-performance-analyzer/

it's quite absurd to measure time with a parallelization suite, but well: it works.
Why is it absurd? The solution is cross platform, simple, accurate, and even works with threading. What's not to like?

Collectives™ on Stack Overflow

How to calculate time execution and cpu speding for a function in C++

3 Answers 3

4 Comments

Comments

2 Comments

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

4 Comments

Comments

2 Comments

Linked

Related