Timer.hpp

// Copyright (c) 2017-2026, University of Cincinnati, developed by Henry Schreiner
// under NSF AWARD 1414736 and by the respective contributors.
// All rights reserved.
//
// SPDX-License-Identifier: BSD-3-Clause
 
#pragma once
 
// IWYU pragma: private, include "CLI/CLI.hpp"
 
#include <cmath>
 
#include <array>
#include <chrono>
#include <cstdio>
#include <functional>
#include <iostream>
#include <string>
#include <utility>
 
namespace CLI {
 
class Timer {
  protected:
    using clock = std::chrono::steady_clock;
 
    using time_point = std::chrono::time_point<clock>;
 
    using time_print_t = std::function<std::string(std::string, std::string)>;
 
    std::string title_;
 
    time_print_t time_print_;
 
    time_point start_;
 
    std::size_t cycles{1};
 
  public:
    static std::string Simple(std::string title, std::string time) { return title + ": " + time; }
 
    static std::string Big(std::string title, std::string time) {
        return std::string("-----------------------------------------\n") + "| " + title + " | Time = " + time + "\n" +
               "-----------------------------------------";
    }
 
  public:
    explicit Timer(std::string title = "Timer", time_print_t time_print = Simple)
        : title_(std::move(title)), time_print_(std::move(time_print)), start_(clock::now()) {}
 
    std::string time_it(std::function<void()> f, double target_time = 1) {
        time_point start = start_;
        double total_time = NAN;
 
        start_ = clock::now();
        std::size_t n = 0;
        do {
            f();
            std::chrono::duration<double> elapsed = clock::now() - start_;
            total_time = elapsed.count();
        } while(n++ < 100u && total_time < target_time);
 
        std::string out = make_time_str(total_time / static_cast<double>(n)) + " for " + std::to_string(n) + " tries";
        start_ = start;
        return out;
    }
 
    std::string make_time_str() const {  // NOLINT(modernize-use-nodiscard)
        time_point stop = clock::now();
        std::chrono::duration<double> elapsed = stop - start_;
        double time = elapsed.count() / static_cast<double>(cycles);
        return make_time_str(time);
    }
 
    // LCOV_EXCL_START
    std::string make_time_str(double time) const {  // NOLINT(modernize-use-nodiscard)
        auto print_it = [](double x, std::string unit) {
            const unsigned int buffer_length = 50;
            std::array<char, buffer_length> buffer;
            std::snprintf(buffer.data(), buffer_length, "%.5g", x);
            return buffer.data() + std::string(" ") + unit;
        };
 
        if(time < .000001)
            return print_it(time * 1000000000, "ns");
        if(time < .001)
            return print_it(time * 1000000, "us");
        if(time < 1)
            return print_it(time * 1000, "ms");
        return print_it(time, "s");
    }
    // LCOV_EXCL_STOP
 
    std::string to_string() const { return time_print_(title_, make_time_str()); }  // NOLINT(modernize-use-nodiscard)
 
    Timer &operator/(std::size_t val) {
        cycles = val;
        return *this;
    }
};
 
class AutoTimer : public Timer {
  public:
    using Timer::Timer;
 
    ~AutoTimer() { std::cout << to_string() << '\n'; }
};
 
}  // namespace CLI
 
inline std::ostream &operator<<(std::ostream &in, const CLI::Timer &timer) { return in << timer.to_string(); }