Stopwatch

C++ implementation of a Stopwatch class

Introduction

This repository is home to a tiny C++ implementation of a stopwatch. It aims at providing an easy-to-use stopwatch. Basically, it's just an API to std::chrono::high_precision_clock. But googling for "std chrono duration_cast", "std chrono time_point template" for the 271st time -rough estimation-, finally convinced me that I need to write this code snippet. Here I'm sharing the result.

Installation

Download the header Stopwatch.hpp from the include folder of this repository, include it, and you're ready to go. No dependencies no nothing.

Usage

Info: In /test/main.cpp you'll find a program that combines the following three examples into one main() function. It should be executable as soon as you adapt the include path to "Stopwatch.hpp".

Basics

Suppose you have a loop, a function call or a complete program whose execution time you want to measure.
The Stopwatch class allows you to do this with two lines of code:
Stopwatch my_watch; creates an instance of Stopwatch and starts it.
uint64_t duration_ms = my_watch.elapsed(); returns the elapsed time since the instantiation in milliseconds.

Here's a minimal executable example:

#include <iostream>
#include "Stopwatch.h"

int main(){
  //Namespace alias
  namespace sw = stopwatch;

  //Create and start a stopwatch
  sw::Stopwatch my_watch;

  //Do something time-consuming here...

  //Take the time
  auto duration_ms = my_watch.elapsed();
  std::cout << "Elapsed: " << duration_ms << " milliseconds." << std::endl;
}

Goodies

Additionally, you can start (actually, re-start) the watch manually at any point by calling my_watch.start().
Furthermore, you can get the elapsed time formatted as seconds, milliseconds, microseconds or nanoseconds by passing the respective template-argument to the my_watch.elapsed() call:

#include <iostream>
#include "Stopwatch.h"

int main()
{
   //Namespace alias
   namespace sw = stopwatch;

   //Create a stopwatch..
   sw::Stopwatch my_watch;
   //and (re-)start it
   my_watch.start();

   //Do something time-consuming here...

   //Get elapsed time..
   // .. in nanoseconds
   std::uint64_t elapsed_ns = my_watch.elapsed<sw::ns>();
   // .. in microseconds
   std::uint64_t elapsed_mus = my_watch.elapsed<sw::mus>();
   // .. in milliseconds (default template argument, therefore not needed)
   std::uint64_t elapsed_ms = my_watch.elapsed();
   // .. in seconds
   std::uint64_t elapsed_s = my_watch.elapsed<sw::s>();

   return 0;
}

Taking lap times

Lastly, you can use a Stopwatch to take lap times. Of course this can be done using several stopwatches, but here's the API to do it with only one.
Initialize a stopwatch as before. Every time my_watch.lap(); is called, the watch outputs the elapsed time since the last call to lap(). (Or since the last call of my_watch.start() for the first lap.) The output can be formatted by passing a format template to the lap() call as in the Goodies example (see also code below).
The function my_watch.elapsed_laps<fmt_total, fmt_laps>() returns a pair: The first element is the total elapsed time between my_watch.start() and the last call of my_watch.lap(). The second element is a vector of lap times. The format of the times can be set using the template arguments fmt_total and fmt_laps respectively. This comes in handy if you want to ouput the total time in seconds, but the lap times in milliseconds. The default is fmt_total = MILLISECONDS and fmt_lap = fmt_total.
Finally, some code taking lap times of a loop:

#include <iostream>
#include "Stopwatch.hpp"

int main()
{
   //Namespace alias
   namespace sw = stopwatch;

   //Create and start a stopwatch
   sw::Stopwatch my_watch;

   //Do something time-consuming:
   for(std::size_t i = 1; i <= 500000; i++){
      if( i%10 == 0){
         std::cout << i << std::endl;
      }
      //Take lap time every 100000th iteration
      if( i % 100000 == 0){
        auto lap_ms = my_watch.lap<sw::milliseconds>();
        std::cout << "Lap time in ms: " << lap_ms << std::endl;
      }
   }

   //Get all lap times. The total in seconds, single times in milliseconds
   auto laps = my_watch.elapsed_laps<sw::seconds, sw::milliseconds>();

   //Print to console
   std::cout << "---------------" << std::endl;
   std::cout << "Laps Total: " << laps.first << " sec" << std::endl;
   auto lap_times = laps.second;
   std::cout << "Lap Times [ms]: " << sw::show_times(lap_times);

   return 0;
}

License

Distributed under the MIT Software License (X11 license). (See accompanying file LICENSE.)

gbasler / Stopwatch