external/CLI/Timer.hpp

0001 // Copyright (c) 2017-2020, University of Cincinnati, developed by Henry Schreiner
0002 // under NSF AWARD 1414736 and by the respective contributors.
0003 // All rights reserved.
0004 //
0005 // SPDX-License-Identifier: BSD-3-Clause
0006
0007 #pragma once
0008
0009 // On GCC < 4.8, the following define is often missing. Due to the
0010 // fact that this library only uses sleep_for, this should be safe
0011 #if defined(__GNUC__) && !defined(__clang__) && __GNUC__ < 5 && __GNUC_MINOR__ < 8
0012 #define _GLIBCXX_USE_NANOSLEEP
0013 #endif
0014
0015 #include <array>
0016 #include <chrono>
0017 #include <functional>
0018 #include <iostream>
0019 #include <string>
0020 #include <utility>
0021
0022 namespace CLI {
0023
0024 /// This is a simple timer with pretty printing. Creating the timer starts counting.
0025 class Timer {
0026   protected:
0027     /// This is a typedef to make clocks easier to use
0028     using clock = std::chrono::steady_clock;
0029
0030     /// This typedef is for points in time
0031     using time_point = std::chrono::time_point<clock>;
0032
0033     /// This is the type of a printing function, you can make your own
0034     using time_print_t = std::function<std::string(std::string, std::string)>;
0035
0036     /// This is the title of the timer
0037     std::string title_;
0038
0039     /// This is the function that is used to format most of the timing message
0040     time_print_t time_print_;
0041
0042     /// This is the starting point (when the timer was created)
0043     time_point start_;
0044
0045     /// This is the number of times cycles (print divides by this number)
0046     std::size_t cycles{1};
0047
0048   public:
0049     /// Standard print function, this one is set by default
0050     static std::string Simple(std::string title, std::string time) { return title + ": " + time; }
0051
0052     /// This is a fancy print function with --- headers
0053     static std::string Big(std::string title, std::string time) {
0054         return std::string("-----------------------------------------\n") + "| " + title + " | Time = " + time + "\n" +
0055                "-----------------------------------------";
0056     }
0057
0058   public:
0059     /// Standard constructor, can set title and print function
0060     explicit Timer(std::string title = "Timer", time_print_t time_print = Simple)
0061         : title_(std::move(title)), time_print_(std::move(time_print)), start_(clock::now()) {}
0062
0063     /// Time a function by running it multiple times. Target time is the len to target.
0064     std::string time_it(std::function<void()> f, double target_time = 1) {
0065         time_point start = start_;
0066         double total_time;
0067
0068         start_ = clock::now();
0069         std::size_t n = 0;
0070         do {
0071             f();
0072             std::chrono::duration<double> elapsed = clock::now() - start_;
0073             total_time = elapsed.count();
0074         } while(n++ < 100u && total_time < target_time);
0075
0076         std::string out = make_time_str(total_time / static_cast<double>(n)) + " for " + std::to_string(n) + " tries";
0077         start_ = start;
0078         return out;
0079     }
0080
0081     /// This formats the numerical value for the time string
0082     std::string make_time_str() const {
0083         time_point stop = clock::now();
0084         std::chrono::duration<double> elapsed = stop - start_;
0085         double time = elapsed.count() / static_cast<double>(cycles);
0086         return make_time_str(time);
0087     }
0088
0089     // LCOV_EXCL_START
0090     /// This prints out a time string from a time
0091     std::string make_time_str(double time) const {
0092         auto print_it = [](double x, std::string unit) {
0093             const unsigned int buffer_length = 50;
0094             std::array<char, buffer_length> buffer;
0095             std::snprintf(buffer.data(), buffer_length, "%.5g", x);
0096             return buffer.data() + std::string(" ") + unit;
0097         };
0098
0099         if(time < .000001)
0100             return print_it(time * 1000000000, "ns");
0101         else if(time < .001)
0102             return print_it(time * 1000000, "us");
0103         else if(time < 1)
0104             return print_it(time * 1000, "ms");
0105         else
0106             return print_it(time, "s");
0107     }
0108     // LCOV_EXCL_STOP
0109
0110     /// This is the main function, it creates a string
0111     std::string to_string() const { return time_print_(title_, make_time_str()); }
0112
0113     /// Division sets the number of cycles to divide by (no graphical change)
0114     Timer &operator/(std::size_t val) {
0115         cycles = val;
0116         return *this;
0117     }
0118 };
0119
0120 /// This class prints out the time upon destruction
0121 class AutoTimer : public Timer {
0122   public:
0123     /// Reimplementing the constructor is required in GCC 4.7
0124     explicit AutoTimer(std::string title = "Timer", time_print_t time_print = Simple) : Timer(title, time_print) {}
0125     // GCC 4.7 does not support using inheriting constructors.
0126
0127     /// This destructor prints the string
0128     ~AutoTimer() { std::cout << to_string() << std::endl; }
0129 };
0130
0131 }  // namespace CLI
0132
0133 /// This prints out the time if shifted into a std::cout like stream.
0134 inline std::ostream &operator<<(std::ostream &in, const CLI::Timer &timer) { return in << timer.to_string(); }