include/CLI/Timer.hpp

0001 // Copyright (c) 2017-2026, 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 // IWYU pragma: private, include "CLI/CLI.hpp"
0010
0011 #include <cmath>
0012
0013 #include <array>
0014 #include <chrono>
0015 #include <cstdio>
0016 #include <functional>
0017 #include <iostream>
0018 #include <string>
0019 #include <utility>
0020
0021 namespace CLI {
0022
0023 /// This is a simple timer with pretty printing. Creating the timer starts counting.
0024 class Timer {
0025   protected:
0026     /// This is a typedef to make clocks easier to use
0027     using clock = std::chrono::steady_clock;
0028
0029     /// This typedef is for points in time
0030     using time_point = std::chrono::time_point<clock>;
0031
0032     /// This is the type of a printing function, you can make your own
0033     using time_print_t = std::function<std::string(std::string, std::string)>;
0034
0035     /// This is the title of the timer
0036     std::string title_;
0037
0038     /// This is the function that is used to format most of the timing message
0039     time_print_t time_print_;
0040
0041     /// This is the starting point (when the timer was created)
0042     time_point start_;
0043
0044     /// This is the number of times cycles (print divides by this number)
0045     std::size_t cycles{1};
0046
0047   public:
0048     /// Standard print function, this one is set by default
0049     static std::string Simple(std::string title, std::string time) { return title + ": " + time; }
0050
0051     /// This is a fancy print function with --- headers
0052     static std::string Big(std::string title, std::string time) {
0053         return std::string("-----------------------------------------\n") + "| " + title + " | Time = " + time + "\n" +
0054                "-----------------------------------------";
0055     }
0056
0057   public:
0058     /// Standard constructor, can set title and print function
0059     explicit Timer(std::string title = "Timer", time_print_t time_print = Simple)
0060         : title_(std::move(title)), time_print_(std::move(time_print)), start_(clock::now()) {}
0061
0062     /// Time a function by running it multiple times. Target time is the len to target.
0063     std::string time_it(std::function<void()> f, double target_time = 1) {
0064         time_point start = start_;
0065         double total_time = NAN;
0066
0067         start_ = clock::now();
0068         std::size_t n = 0;
0069         do {
0070             f();
0071             std::chrono::duration<double> elapsed = clock::now() - start_;
0072             total_time = elapsed.count();
0073         } while(n++ < 100u && total_time < target_time);
0074
0075         std::string out = make_time_str(total_time / static_cast<double>(n)) + " for " + std::to_string(n) + " tries";
0076         start_ = start;
0077         return out;
0078     }
0079
0080     /// This formats the numerical value for the time string
0081     std::string make_time_str() const {  // NOLINT(modernize-use-nodiscard)
0082         time_point stop = clock::now();
0083         std::chrono::duration<double> elapsed = stop - start_;
0084         double time = elapsed.count() / static_cast<double>(cycles);
0085         return make_time_str(time);
0086     }
0087
0088     // LCOV_EXCL_START
0089     /// This prints out a time string from a time
0090     std::string make_time_str(double time) const {  // NOLINT(modernize-use-nodiscard)
0091         auto print_it = [](double x, std::string unit) {
0092             const unsigned int buffer_length = 50;
0093             std::array<char, buffer_length> buffer;
0094             std::snprintf(buffer.data(), buffer_length, "%.5g", x);
0095             return buffer.data() + std::string(" ") + unit;
0096         };
0097
0098         if(time < .000001)
0099             return print_it(time * 1000000000, "ns");
0100         if(time < .001)
0101             return print_it(time * 1000000, "us");
0102         if(time < 1)
0103             return print_it(time * 1000, "ms");
0104         return print_it(time, "s");
0105     }
0106     // LCOV_EXCL_STOP
0107
0108     /// This is the main function, it creates a string
0109     std::string to_string() const { return time_print_(title_, make_time_str()); }  // NOLINT(modernize-use-nodiscard)
0110
0111     /// Division sets the number of cycles to divide by (no graphical change)
0112     Timer &operator/(std::size_t val) {
0113         cycles = val;
0114         return *this;
0115     }
0116 };
0117
0118 /// This class prints out the time upon destruction
0119 class AutoTimer : public Timer {
0120   public:
0121     using Timer::Timer;
0122
0123     /// This destructor prints the string
0124     ~AutoTimer() { std::cout << to_string() << '\n'; }
0125 };
0126
0127 }  // namespace CLI
0128
0129 /// This prints out the time if shifted into a std::cout like stream.
0130 inline std::ostream &operator<<(std::ostream &in, const CLI::Timer &timer) { return in << timer.to_string(); }