Program Listing for File timer.h

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#pragma once

#include <iostream>
#include <sstream>
#include <chrono>
#include <ctime>

namespace marian {
namespace timer {

// Helper function to get the current date and time
static inline std::string currentDate() {
  std::time_t now = std::chrono::system_clock::to_time_t(std::chrono::system_clock::now());
  char date[100] = {0};
  std::strftime(date, sizeof(date), "%F %X %z", std::localtime(&now));
  return date;
}

// Timer measures elapsed time.
class Timer {
protected:
  using clock = std::chrono::steady_clock;
  using time_point = std::chrono::time_point<clock>;
  using duration = std::chrono::nanoseconds;

  time_point start_;     // Starting time point
  bool stopped_{false};  // Indicator if the timer has been stopped
  duration time_;        // Time duration from start() to stop()

public:
  // Create and start the timer
  Timer() : start_(clock::now()) {}

  // Restart the timer. It is not resuming
  void start() {
    stopped_ = false;
    start_ = clock::now();
  }

  // Stop the timer
  void stop() {
    if(stopped_)
      return;
    stopped_ = true;
    time_ = clock::now() - start_;
  }

  // Check if the timer has been stopped
  bool stopped() const { return stopped_; }

  // Get the time elapsed without stopping the timer.
  // If the template type is not specified, it returns the time counts as represented by
  // std::chrono::seconds
  template <class Duration = std::chrono::seconds>
  double elapsed() const {
    using duration_double = std::chrono::duration<double, typename Duration::period>;
    if(stopped_)
      return std::chrono::duration_cast<duration_double>(time_).count();
    return std::chrono::duration_cast<duration_double>(clock::now() - start_).count();
  }

  // Default desctructor
  virtual ~Timer() {}
};

// Automatic timer displays timing information on the standard output stream when it is destroyed
class AutoTimer : public Timer {
public:
  // Create and start the timer
  AutoTimer() : Timer() {}

  // Stop the timer and display time elapsed on std::cout
  ~AutoTimer() {
    stop();
    std::cout << "Time: " << elapsed() << "s wall" << std::endl;
  }
};

// std::chrono::steady_clock seems to be the right choice here.
using CPUTimer = Timer;


}  // namespace timer
}  // namespace marian