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

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#include        "ClockCycleCounter.h"

#include        <cassert>

namespace stopwatch
{

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/*
==============================================================================
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);
}

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#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

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