I recently needed to profile some C++ code that was taking longer than expected to run. The code was running on a machine without a profiler, so I wrote a handy Timer class that dumps nested timings of each method. You can initialize it to write either to a file or to std::cout if the machine has a console.

I originally thought of this as a ‘Poor Man’s Profiler’, but having used it there are real benefits to taking the trouble to instrument your own code – you can use the file dumps to swiftly compare performance between code changes; you can print out performance statistics and take along to meetings.

#include <iostream> #include <chrono> class TimerOutput { public: TimerOutput( const std::string file_path = "" ) : file_path_( file_path ) { if ( !file_path_.empty() ) { file_.open( file_path_ ); } } std::ostream& Stream() { if (file_path_.empty() ) return std::cout; else return file_; } private: std::string file_path_; std::ofstream file_; }; class Timer { public: Timer( const std::string& description ) : description_(description), start_(std::chrono::system_clock::now()) { applyIndent(); timer_output_->Stream() << "Start " << description_.c_str() << "

"; ++indent; } ~Timer() { --indent; const std::chrono::time_point<std::chrono::system_clock> finish = std::chrono::system_clock::now(); auto milliseconds = std::chrono::duration_cast<std::chrono::milliseconds>(finish - start_).count(); applyIndent(); timer_output_->Stream() << "Finished " << description_.c_str() << ", took " << milliseconds << " (ms)" << "

"; } private: void applyIndent() const { for ( size_t i = 0; i < indent; ++i ) { timer_output_->Stream() << "--"; } } static size_t indent; static TimerOutput* timer_output_; std::string description_; const std::chrono::time_point<std::chrono::system_clock> start_; }; #define INITIALIZE_PROFILING_TO_CONSOLE() \ TimerOutput timer_output; \ size_t Timer::indent = 0; \ TimerOutput* Timer::timer_output_ = &timer_output; #define INITIALIZE_PROFILING_TO_FILE( path ) \ TimerOutput timer_output( path ); \ size_t Timer::indent = 0; \ TimerOutput* Timer::timer_output_ = &timer_output; #define TIME( description, f ) \ { \ Timer profiler( description ); \ f; \ }

The obvious limitation of my solution is that it uses a class static to achieve the levels of nesting, so it won’t work on multi-threaded code – but it was great for my purposes. Here’s some sample code that shows it in action:





#include "stdafx.h" #include <thread> #include <fstream> #include "..\MusingStudio\Profiler.h" //INITIALIZE_PROFILING_TO_CONSOLE() INITIALIZE_PROFILING_TO_FILE( "c:/temp/timings.txt" ) void method2() { TIME( "method2", std::chrono::milliseconds short_wait( 5 ); std::this_thread::sleep_for( short_wait ); ) } void method1() { TIME( "method1", TIME( "loop", for ( int i = 0; i < 5; ++i ) { method2(); } ) TIME( "expensive algorithm", std::chrono::milliseconds wait( 100 ); std::this_thread::sleep_for( wait ); ) ) } void method3() { TIME( "method3", std::chrono::milliseconds long_wait( 500 ); std::this_thread::sleep_for( long_wait ); ) } int main(int argc, char* argv[]) { TIME( "main", method1(); method3(); ) return 0; }

Here’s the output from the sample code:

