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