timer.hh

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// -*- tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
// vi: set et ts=4 sw=2 sts=2:
// SPDX-FileCopyrightInfo: Copyright © DUNE Project contributors, see file LICENSE.md in module root
// SPDX-License-Identifier: LicenseRef-GPL-2.0-only-with-DUNE-exception
#ifndef DUNE_TIMER_HH
#define DUNE_TIMER_HH

#include <chrono>

namespace Dune {

  class Timer
  {
    using Clock = std::chrono::high_resolution_clock;
    using Units = std::chrono::duration<double>; // seconds stored as double
  public:

    Timer (bool startImmediately=true) noexcept
    {
      isRunning_ = startImmediately;
      reset();
    }

    void reset() noexcept
    {
      sumElapsed_ = std::chrono::seconds{0};
      storedLastElapsed_ = std::chrono::seconds{0};
      cstart = Clock::now();
    }


    void start() noexcept
    {
      if (not (isRunning_))
      {
        cstart = Clock::now();
        isRunning_ = true;
      }
    }


    double elapsed () const noexcept
    {
      return durationCast(rawElapsed());
    }

    double lastElapsed () const noexcept
    {
      return durationCast(rawLastElapsed());
    }

    double stop() noexcept
    {
      if (isRunning_)
      {
        // update storedLastElapsed_ and  sumElapsed_ and stop timer
        storedLastElapsed_ = rawLastElapsed();
        sumElapsed_ += storedLastElapsed_;
        isRunning_ = false;
      }
      return elapsed();
    }


  private:

    bool isRunning_;
    Clock::duration sumElapsed_;
    Clock::duration storedLastElapsed_;

    Clock::duration rawElapsed () const noexcept
    {
      // if timer is running add the time elapsed since last start to sum
      if (isRunning_)
        return sumElapsed_ + rawLastElapsed();

      return sumElapsed_;
    }

    Clock::duration rawLastElapsed () const noexcept
    {
      // if timer is running return the current value
      if (isRunning_)
        return Clock::now() - cstart;

      // if timer is not running return stored value from last run
      return storedLastElapsed_;
    }

    double durationCast(Clock::duration duration) const noexcept {
      return std::chrono::duration_cast<Units>(duration).count();
    }

    Clock::time_point cstart;
  }; // end class Timer

} // end namespace

#endif