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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;
}
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