Qt Reference Documentation

# ClockCycleCounter.cpp Example File

demos/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 \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*/