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/*

 * $Id$

 * Portable Audio I/O Library CPU Load measurement functions

 * Portable CPU load measurement facility.

 *

 * Based on the Open Source API proposed by Ross Bencina

 * Copyright (c) 2002 Ross Bencina

 *

 * Permission is hereby granted, free of charge, to any person obtaining

 * a copy of this software and associated documentation files

 * (the "Software"), to deal in the Software without restriction,

 * including without limitation the rights to use, copy, modify, merge,

 * publish, distribute, sublicense, and/or sell copies of the Software,

 * and to permit persons to whom the Software is furnished to do so,

 * subject to the following conditions:

 *

 * The above copyright notice and this permission notice shall be

 * included in all copies or substantial portions of the Software.

 *

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,

 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF

 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.

 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR

 * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF

 * CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION

 * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

 */

/*

 * The text above constitutes the entire PortAudio license; however, 

 * the PortAudio community also makes the following non-binding requests:

 *

 * Any person wishing to distribute modifications to the Software is

 * requested to send the modifications to the original developer so that

 * they can be incorporated into the canonical version. It is also 

 * requested that these non-binding requests be included along with the 

 * license above.

 */

/** @file

 @ingroup common_src

 @brief Functions to assist in measuring the CPU utilization of a callback

 stream. Used to implement the Pa_GetStreamCpuLoad() function.

 @todo Dynamically calculate the coefficients used to smooth the CPU Load

 Measurements over time to provide a uniform characterisation of CPU Load

 independent of rate at which PaUtil_BeginCpuLoadMeasurement /

 PaUtil_EndCpuLoadMeasurement are called. see http://www.portaudio.com/trac/ticket/113

*/

#include "pa_cpuload.h"

#include <assert.h>

#include "pa_util.h"   /* for PaUtil_GetTime() */

void PaUtil_InitializeCpuLoadMeasurer( PaUtilCpuLoadMeasurer* measurer, double sampleRate )

{

    assert( sampleRate > 0 );

    measurer->samplingPeriod = 1. / sampleRate;

    measurer->averageLoad = 0.;

}

void PaUtil_ResetCpuLoadMeasurer( PaUtilCpuLoadMeasurer* measurer )

{

    measurer->averageLoad = 0.;

}

void PaUtil_BeginCpuLoadMeasurement( PaUtilCpuLoadMeasurer* measurer )

{

    measurer->measurementStartTime = PaUtil_GetTime();

}

void PaUtil_EndCpuLoadMeasurement( PaUtilCpuLoadMeasurer* measurer, unsigned long framesProcessed )

{

    double measurementEndTime, secondsFor100Percent, measuredLoad;

    if( framesProcessed > 0 ){

        measurementEndTime = PaUtil_GetTime();

        assert( framesProcessed > 0 );

        secondsFor100Percent = framesProcessed * measurer->samplingPeriod;

        measuredLoad = (measurementEndTime - measurer->measurementStartTime) / secondsFor100Percent;

        /* Low pass filter the calculated CPU load to reduce jitter using a simple IIR low pass filter. */

        /** FIXME @todo these coefficients shouldn't be hardwired see: http://www.portaudio.com/trac/ticket/113 */

#define LOWPASS_COEFFICIENT_0   (0.9)

#define LOWPASS_COEFFICIENT_1   (0.99999 - LOWPASS_COEFFICIENT_0)

        measurer->averageLoad = (LOWPASS_COEFFICIENT_0 * measurer->averageLoad) +

                               (LOWPASS_COEFFICIENT_1 * measuredLoad);

    }

}

double PaUtil_GetCpuLoad( PaUtilCpuLoadMeasurer* measurer )

{

    return measurer->averageLoad;

}