////////////////////////////////////////////////////////////////////////////////
//
// The University of Illinois/NCSA
// Open Source License (NCSA)
//
// Copyright (c) 2014-2015, Advanced Micro Devices, Inc. All rights reserved.
//
// Developed by:
//
//                 AMD Research and AMD HSA Software Development
//
//                 Advanced Micro Devices, Inc.
//
//                 www.amd.com
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to
// deal with the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
//  - Redistributions of source code must retain the above copyright notice,
//    this list of conditions and the following disclaimers.
//  - Redistributions in binary form must reproduce the above copyright
//    notice, this list of conditions and the following disclaimers in
//    the documentation and/or other materials provided with the distribution.
//  - Neither the names of Advanced Micro Devices, Inc,
//    nor the names of its contributors may be used to endorse or promote
//    products derived from this Software without specific prior written
//    permission.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
// THE CONTRIBUTORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
// OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS WITH THE SOFTWARE.
//
////////////////////////////////////////////////////////////////////////////////

#include "core/util/timer.h"

namespace timer {

accurate_clock::init::init() {
  freq = os::AccurateClockFrequency();
  accurate_clock::period_ns = 1e9 / double(freq);
}

// Calibrates the fast clock using the accurate clock.
fast_clock::init::init() {
  typedef accurate_clock clock;
  clock::duration delay(std::chrono::milliseconds(1));

  // calibrate clock
  fast_clock::raw_rep min = 0;
  clock::duration elapsed = clock::duration::max();

  do {
    for (int t = 0; t < 10; t++) {
      fast_clock::raw_rep r1, r2;
      clock::time_point t0, t1, t2, t3;

      t0 = clock::now();
      std::atomic_signal_fence(std::memory_order_acq_rel);
      r1 = fast_clock::raw_now();
      std::atomic_signal_fence(std::memory_order_acq_rel);
      t1 = clock::now();
      std::atomic_signal_fence(std::memory_order_acq_rel);

      do {
        t2 = clock::now();
      } while (t2 - t1 < delay);

      std::atomic_signal_fence(std::memory_order_acq_rel);
      r2 = fast_clock::raw_now();
      std::atomic_signal_fence(std::memory_order_acq_rel);
      t3 = clock::now();

      // If elapsed time is shorter than last recorded time and both the start
      // and end times are confirmed correlated then record the clock readings.
      // This protects against inaccuracy due to thread switching
      if ((t3 - t1 < elapsed) && ((t1 - t0) * 10 < (t2 - t1)) &&
          ((t3 - t2) * 10 < (t2 - t1))) {
        elapsed = t3 - t1;
        min = r2 - r1;
      }
    }
    delay += delay;
  } while (min < 1000);

  fast_clock::freq = double(min) / duration_in_seconds(elapsed);
  fast_clock::period_ps = 1e12 / fast_clock::freq;
}

double accurate_clock::period_ns;
accurate_clock::raw_frequency accurate_clock::freq;
accurate_clock::init accurate_clock::accurate_clock_init;

double fast_clock::period_ps;
fast_clock::raw_frequency fast_clock::freq;
fast_clock::init fast_clock::fast_clock_init;
}