include/CLI/Timer.hpp

0001 // Copyright (c) 2017-2023, 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 <cmath>
0016
0017 #include <array>
0018 #include <chrono>
0019 #include <functional>
0020 #include <iostream>
0021 #include <string>
0022 #include <utility>
0023
0024 namespace CLI {
0025
0026 /// This is a simple timer with pretty printing. Creating the timer starts counting.
0027 class Timer {
0028   protected:
0029     /// This is a typedef to make clocks easier to use
0030     using clock = std::chrono::steady_clock;
0031
0032     /// This typedef is for points in time
0033     using time_point = std::chrono::time_point<clock>;
0034
0035     /// This is the type of a printing function, you can make your own
0036     using time_print_t = std::function<std::string(std::string, std::string)>;
0037
0038     /// This is the title of the timer
0039     std::string title_;
0040
0041     /// This is the function that is used to format most of the timing message
0042     time_print_t time_print_;
0043
0044     /// This is the starting point (when the timer was created)
0045     time_point start_;
0046
0047     /// This is the number of times cycles (print divides by this number)
0048     std::size_t cycles{1};
0049
0050   public:
0051     /// Standard print function, this one is set by default
0052     static std::string Simple(std::string title, std::string time) { return title + ": " + time; }
0053
0054     /// This is a fancy print function with --- headers
0055     static std::string Big(std::string title, std::string time) {
0056         return std::string("-----------------------------------------\n") + "| " + title + " | Time = " + time + "\n" +
0057                "-----------------------------------------";
0058     }
0059
0060   public:
0061     /// Standard constructor, can set title and print function
0062     explicit Timer(std::string title = "Timer", time_print_t time_print = Simple)
0063         : title_(std::move(title)), time_print_(std::move(time_print)), start_(clock::now()) {}
0064
0065     /// Time a function by running it multiple times. Target time is the len to target.
0066     std::string time_it(std::function<void()> f, double target_time = 1) {
0067         time_point start = start_;
0068         double total_time = NAN;
0069
0070         start_ = clock::now();
0071         std::size_t n = 0;
0072         do {
0073             f();
0074             std::chrono::duration<double> elapsed = clock::now() - start_;
0075             total_time = elapsed.count();
0076         } while(n++ < 100u && total_time < target_time);
0077
0078         std::string out = make_time_str(total_time / static_cast<double>(n)) + " for " + std::to_string(n) + " tries";
0079         start_ = start;
0080         return out;
0081     }
0082
0083     /// This formats the numerical value for the time string
0084     std::string make_time_str() const {  // NOLINT(modernize-use-nodiscard)
0085         time_point stop = clock::now();
0086         std::chrono::duration<double> elapsed = stop - start_;
0087         double time = elapsed.count() / static_cast<double>(cycles);
0088         return make_time_str(time);
0089     }
0090
0091     // LCOV_EXCL_START
0092     /// This prints out a time string from a time
0093     std::string make_time_str(double time) const {  // NOLINT(modernize-use-nodiscard)
0094         auto print_it = [](double x, std::string unit) {
0095             const unsigned int buffer_length = 50;
0096             std::array<char, buffer_length> buffer;
0097             std::snprintf(buffer.data(), buffer_length, "%.5g", x);
0098             return buffer.data() + std::string(" ") + unit;
0099         };
0100
0101         if(time < .000001)
0102             return print_it(time * 1000000000, "ns");
0103         if(time < .001)
0104             return print_it(time * 1000000, "us");
0105         if(time < 1)
0106             return print_it(time * 1000, "ms");
0107         return print_it(time, "s");
0108     }
0109     // LCOV_EXCL_STOP
0110
0111     /// This is the main function, it creates a string
0112     std::string to_string() const { return time_print_(title_, make_time_str()); }  // NOLINT(modernize-use-nodiscard)
0113
0114     /// Division sets the number of cycles to divide by (no graphical change)
0115     Timer &operator/(std::size_t val) {
0116         cycles = val;
0117         return *this;
0118     }
0119 };
0120
0121 /// This class prints out the time upon destruction
0122 class AutoTimer : public Timer {
0123   public:
0124     /// Reimplementing the constructor is required in GCC 4.7
0125     explicit AutoTimer(std::string title = "Timer", time_print_t time_print = Simple) : Timer(title, time_print) {}
0126     // GCC 4.7 does not support using inheriting constructors.
0127
0128     /// This destructor prints the string
0129     ~AutoTimer() { std::cout << to_string() << std::endl; }
0130 };
0131
0132 }  // namespace CLI
0133
0134 /// This prints out the time if shifted into a std::cout like stream.
0135 inline std::ostream &operator<<(std::ostream &in, const CLI::Timer &timer) { return in << timer.to_string(); }