- Qt 5.5
- Qt Multimedia
- Spectrum Example
- ClockCycleCounter.cpp Example File
- Qt 5.5.1 Reference Documentation

# ClockCycleCounter.cpp Example File

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