ClockCycleCounter.cpp Example File

  /*****************************************************************************

          ClockCycleCounter.cpp
          Copyright (c) 2003 Laurent de Soras

  --- Legal stuff ---

  This library is free software; you can redistribute it and/or
  modify it under the terms of the GNU Lesser General Public
  License as published by the Free Software Foundation; either
  version 2.1 of the License, or (at your option) any later version.

  This library is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public
  License along with this library; if not, write to the Free Software
  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

  *Tab=3***********************************************************************/

  #if defined (_MSC_VER)
          #pragma warning (1 : 4130) // "'operator' : logical operation on address of string constant"
          #pragma warning (1 : 4223) // "nonstandard extension used : non-lvalue array converted to pointer"
          #pragma warning (1 : 4705) // "statement has no effect"
          #pragma warning (1 : 4706) // "assignment within conditional expression"
          #pragma warning (4 : 4786) // "identifier was truncated to '255' characters in the debug information"
          #pragma warning (4 : 4800) // "forcing value to bool 'true' or 'false' (performance warning)"
          #pragma warning (4 : 4355) // "'this' : used in base member initializer list"
  #endif

  /*\\\ INCLUDE FILES \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*/

  #include        "ClockCycleCounter.h"

  #include        <cassert>

  namespace stopwatch
  {

  /*\\\ PUBLIC \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*/

  /*
  ==============================================================================
  Name: ctor
  Description:
          The first object constructed initialise global data. This first
          construction may be a bit slow.
  Throws: Nothing
  ==============================================================================
  */

  ClockCycleCounter::ClockCycleCounter ()
  :       _start_time (0)
  ,       _state (0)
  ,       _best_score (-1)
  {
          if (! _init_flag)
          {
                  // Should be executed in this order
                  compute_clk_mul ();
                  compute_measure_time_total ();
                  compute_measure_time_lap ();

                  // Restores object state
                  _start_time = 0;
                  _state      = 0;
                  _best_score = -1;

                  _init_flag = true;
          }
  }

  /*
  ==============================================================================
  Name: get_time_total
  Description:
          Gives the time elapsed between the latest stop_lap() and start() calls.
  Returns:
          The duration, in clock cycles.
  Throws: Nothing
  ==============================================================================
  */

  Int64   ClockCycleCounter::get_time_total () const
  {
          const Int64             duration = _state - _start_time;
          assert (duration >= 0);

          const Int64             t = max (
                  duration - _measure_time_total,
                  static_cast <Int64> (0)
          );

          return (t * _clk_mul);
  }

  /*
  ==============================================================================
  Name: get_time_best_lap
  Description:
          Gives the smallest time between two consecutive stop_lap() or between
          the stop_lap() and start(). The value is reset by a call to start().
          Call this function only after a stop_lap().
          The time is amputed from the duration of the stop_lap() call itself.
  Returns:
          The smallest duration, in clock cycles.
  Throws: Nothing
  ==============================================================================
  */

  Int64   ClockCycleCounter::get_time_best_lap () const
  {
          assert (_best_score >= 0);

          const Int64             t1 = max (
                  _best_score - _measure_time_lap,
                  static_cast <Int64> (0)
          );
          const Int64             t = min (t1, get_time_total ());

          return (t * _clk_mul);
  }

  /*\\\ PROTECTED \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*/

  /*\\\ PRIVATE \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*/

  #if defined (__MACOS__)

  static inline double    stopwatch_ClockCycleCounter_get_time_s ()
  {
          const Nanoseconds       ns = AbsoluteToNanoseconds (UpTime ());

          return (ns.hi * 4294967296e-9 + ns.lo * 1e-9);
  }

  #endif  // __MACOS__

  /*
  ==============================================================================
  Name: compute_clk_mul
  Description:
          This function, only for PowerPC/MacOS computers, computes the multiplier
          required to deduce clock cycles from the internal counter.
  Throws: Nothing
  ==============================================================================
  */

  void    ClockCycleCounter::compute_clk_mul ()
  {
          assert (! _init_flag);

  #if defined (__MACOS__)

          long                            clk_speed_mhz = CurrentProcessorSpeed ();
          const Int64             clk_speed =
                  static_cast <Int64> (clk_speed_mhz) * (1000L*1000L);

          const double    start_time_s = stopwatch_ClockCycleCounter_get_time_s ();
          start ();

          const double    duration = 0.01;        // Seconds
          while (stopwatch_ClockCycleCounter_get_time_s () - start_time_s < duration)
          {
                  continue;
          }

          const double    stop_time_s = stopwatch_ClockCycleCounter_get_time_s ();
          stop ();

          const double    diff_time_s = stop_time_s - start_time_s;
          const double    nbr_cycles = diff_time_s * static_cast <double> (clk_speed);

          const Int64             diff_time_c = _state - _start_time;
          const double    clk_mul = nbr_cycles / static_cast <double> (diff_time_c);

          _clk_mul = round_int (clk_mul);

  #endif  // __MACOS__
  }

  void    ClockCycleCounter::compute_measure_time_total ()
  {
          start ();
          spend_time ();

          Int64                           best_result = 0x7FFFFFFFL;      // Should be enough
          long                            nbr_tests = 100;
          for (long cnt = 0; cnt < nbr_tests; ++cnt)
          {
                  start ();
                  stop_lap ();
                  const Int64             duration = _state - _start_time;
                  best_result = min (best_result, duration);
          }

          _measure_time_total = best_result;
  }

  /*
  ==============================================================================
  Name: compute_measure_time_lap
  Description:
          Computes the duration of one stop_lap() call and store it. It will be used
          later to get the real duration of the measured operation (by substracting
          the measurement duration).
  Throws: Nothing
  ==============================================================================
  */

  void    ClockCycleCounter::compute_measure_time_lap ()
  {
          start ();
          spend_time ();

          long                            nbr_tests = 10;
          for (long cnt = 0; cnt < nbr_tests; ++cnt)
          {
                  stop_lap ();
                  stop_lap ();
                  stop_lap ();
                  stop_lap ();
          }

          _measure_time_lap = _best_score;
  }

  void    ClockCycleCounter::spend_time ()
  {
          const Int64             nbr_clocks = 500;       // Number of clock cycles to spend

          const Int64             start = read_clock_counter ();
          Int64                           current;

          do
          {
                  current = read_clock_counter ();
          }
          while ((current - start) * _clk_mul < nbr_clocks);
  }

  Int64   ClockCycleCounter::_measure_time_total = 0;
  Int64   ClockCycleCounter::_measure_time_lap = 0;
  int     ClockCycleCounter::_clk_mul = 1;
  bool    ClockCycleCounter::_init_flag = false;

  }       // namespace stopwatch

  /*\\\ EOF \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*/