How to calculate execution time in milliseconds

Question

I'm pretty new to C++, I need to print the execution time of my program in milliseconds with 4 digits (X.XXX) - I tried to use

double start_s=clock();
// my program here
double stop_s=clock();
cout << "time: " << (stop_s) << endl;

I got 0. What am I doing wrong? Btw I am using (and have to use, college project) VS2010, so chrono is not an option.

`clock` is very primitive. Use [`std::chrono`](http://en.cppreference.com/w/cpp/chrono) instead. — Mark Ransom, Mar 16 '16 at 17:22

ForceBru · Answer 1 · 2017-05-26T06:58:04.517

19

Use std::chrono::high_resolution_clock from the chrono header.

auto started = std::chrono::high_resolution_clock::now();
DoWork();
auto done = std::chrono::high_resolution_clock::now();

std::cout << std::chrono::duration_cast<std::chrono::milliseconds>(done-started).count();

You can also cast to std::chrono::seconds or std::chrono::nanoseconds if you wish.

Here's a tutorial on measuring execution time with chrono.

Edit: if your compiler doesn't support chrono, then ~~get a newer one~~ take a look at src/ptimer.c in the source code of wget. It works on Windows and Linux and uses native API.

edited May 26 '17 at 06:58

answered Mar 16 '16 at 17:22

ForceBru

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Another example is here: http://www.cplusplus.com/reference/chrono/high_resolution_clock/now/ – yasouser Mar 16 '16 at 17:25
@yasouser, yeah, I was just going to include this link as well. – ForceBru Mar 16 '16 at 17:25
I'm using VS2010 and can't find the chrono header. Does this make sense? – Gilzy Mar 16 '16 at 17:33
Just googled it and yep, VS2010 doesn't have the chrono header, unfortunately my college forces me to use VS 2010. – Gilzy Mar 16 '16 at 17:35
@Gilzy, does it have C++11 support? – ForceBru Mar 16 '16 at 17:36
Partly, It doesn't recognize the chrono header though. – Gilzy Mar 16 '16 at 17:38
@Gilzy, that's bad. Maybe your college wants you to learn some Windows API? All in all, you won't achieve such precision with neither `clock`, nor `time`. – ForceBru Mar 16 '16 at 17:40
@Gilzy, I think there is a solution. Please take a look at my updated answer. – ForceBru Mar 16 '16 at 17:48
@yasouser That linked example is in seconds. it does not address the question – KansaiRobot May 30 '21 at 13:35

How to calculate execution time in milliseconds

1 Answers1