Qt 5.9 | Qt Multimedia | Spectrum Example | ClockCycleCounter.cpp Example File

Qt 5.9.4 Reference Documentation

# ClockCycleCounter.cpp Example File

multimedia/spectrum/3rdparty/fftreal/stopwatch/ClockCycleCounter.cpp

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

              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 \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*/