C++实现统计代码运行时间的示例详解

// Copyright Ingo Proff 2017. // https://github.com/CrikeeIP/Stopwatch // Distributed under the MIT Software License (X11 license). // (See accompanying file LICENSE) #pragma once #include  #include  #include  namespace stopwatch{ class Stopwatch{ public: enum TimeFormat{ NANOSECONDS, MICROSECONDS, MILLISECONDS, SECONDS }; Stopwatch(): start_time(), laps({}) { start(); } void start(){ start_time = std::chrono::high_resolution_clock::now(); laps = {start_time}; } template std::uint64_t lap(){ const auto t = std::chrono::high_resolution_clock::now(); const auto last_r = laps.back(); laps.push_back( t ); return ticks(last_r, t); } template std::uint64_t elapsed(){ const auto end_time = std::chrono::high_resolution_clock::now(); return ticks(start_time, end_time); } template std::pair> elapsed_laps(){ std::vector lap_times; lap_times.reserve(laps.size()-1); for( std::size_t idx = 0; idx <= laps.size()-2; idx++){ const auto lap_end = laps[idx+1]; const auto lap_start = laps[idx]; lap_times.push_back( ticks(lap_start, lap_end) ); } return { ticks(start_time, laps.back()), lap_times }; } private: typedef std::chrono::time_point time_pt; time_pt start_time; std::vector laps; template static std::uint64_t ticks( const time_pt& start_time, const time_pt& end_time){ const auto duration = end_time - start_time; const std::uint64_t ns_count = std::chrono::duration_cast(duration).count(); switch(fmt){ case TimeFormat::NANOSECONDS: { return ns_count; } case TimeFormat::MICROSECONDS: { std::uint64_t up = ((ns_count/100)%10 >= 5) ? 1 : 0; const auto mus_count = (ns_count /1000) + up; return mus_count; } case TimeFormat::MILLISECONDS: { std::uint64_t up = ((ns_count/100000)%10 >= 5) ? 1 : 0; const auto ms_count = (ns_count /1000000) + up; return ms_count; } case TimeFormat::SECONDS: { std::uint64_t up = ((ns_count/100000000)%10 >= 5) ? 1 : 0; const auto s_count = (ns_count /1000000000) + up; return s_count; } } } }; constexpr Stopwatch::TimeFormat ns = Stopwatch::TimeFormat::NANOSECONDS; constexpr Stopwatch::TimeFormat mus = Stopwatch::TimeFormat::MICROSECONDS; constexpr Stopwatch::TimeFormat ms = Stopwatch::TimeFormat::MILLISECONDS; constexpr Stopwatch::TimeFormat s = Stopwatch::TimeFormat::SECONDS; constexpr Stopwatch::TimeFormat nanoseconds = Stopwatch::TimeFormat::NANOSECONDS; constexpr Stopwatch::TimeFormat microseconds = Stopwatch::TimeFormat::MICROSECONDS; constexpr Stopwatch::TimeFormat milliseconds = Stopwatch::TimeFormat::MILLISECONDS; constexpr Stopwatch::TimeFormat seconds = Stopwatch::TimeFormat::SECONDS; std::string show_times( const std::vector& times ){ std::string result("{"); for( const auto& t : times ){ result += std::to_string(t) + ","; } result.back() = static_cast('}'); return result; } } 

//创建一个stopwatch sw::Stopwatch my_watch; my_watch.start(); //Do something time-consuming here... //纳秒 std::uint64_t elapsed_ns = my_watch.elapsed(); //微秒 std::uint64_t elapsed_mus = my_watch.elapsed(); //毫秒 std::uint64_t elapsed_ms = my_watch.elapsed(); //秒 std::uint64_t elapsed_s = my_watch.elapsed(); 

#ifndef __STOPWATCH_H__ #define __STOPWATCH_H__ #if defined(_MSC_VER) || defined(__MINGW32__) || defined(WIN32) #include  #else #include  #endif class StopWatch { public: StopWatch(); ~StopWatch(); //开启计时 void Start(); //暂停计时 void Stop(); //重新计时 void ReStart(); //微秒 double Elapsed(); //毫秒 double ElapsedMS(); //秒 double ElapsedSecond(); private: long long elapsed_; #if defined(_MSC_VER) || defined(__MINGW32__) || defined(WIN32) LARGE_INTEGER start_; LARGE_INTEGER stop_; LARGE_INTEGER frequency_; #else typedef std::chrono::high_resolution_clock Clock; typedef std::chrono::microseconds MicroSeconds; std::chrono::steady_clock::time_point start_; std::chrono::steady_clock::time_point stop_; #endif }; #endif // __STOPWATCH_H__ 

#include "StopWatch.h" #if defined(_MSC_VER) || defined(__MINGW32__) || defined(WIN32) StopWatch::StopWatch():elapsed_(0) { elapsed_ = 0; start_.QuadPart = 0; stop_.QuadPart = 0; QueryPerformanceFrequency(&frequency_); } #else StopWatch::StopWatch():elapsed_(0),start_(MicroSeconds::zero()),stop_(MicroSeconds::zero()) { } #endif StopWatch::~StopWatch() { } void StopWatch::Start() { #if defined(_MSC_VER) || defined(__MINGW32__) || defined(WIN32) QueryPerformanceCounter(&start_); #else start_ = Clock::now(); #endif } void StopWatch::Stop() { #if defined(_MSC_VER) || defined(__MINGW32__) || defined(WIN32) QueryPerformanceCounter(&stop_); elapsed_ += (stop_.QuadPart - start_.QuadPart) * 1000000 / frequency_.QuadPart; #else stop_ = Clock::now(); elapsed_ = std::chrono::duration_cast(stop_ - start_).count(); #endif } void StopWatch::ReStart() { elapsed_ = 0; Start(); } double StopWatch::Elapsed() { return static_cast(elapsed_); } double StopWatch::ElapsedMS() { return elapsed_ / 1000.0; } double StopWatch::ElapsedSecond() { return elapsed_ / 1000000.0; } 

StopWatch sw; sw.Start(); //Do something time-consuming here... sw.Stop(); std::cout << "运行时间：" << sw.ElapsedMS() << "毫秒" << std::endl;