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///////////////////////////////////////////////////////////////////////////
//
// Copyright (c) 2002, Industrial Light & Magic, a division of Lucas
// Digital Ltd. LLC
//
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Industrial Light & Magic nor the names of
// its contributors may be used to endorse or promote products derived
// from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
///////////////////////////////////////////////////////////////////////////
// Primary authors:
// Florian Kainz <kainz@ilm.com>
// Rod Bogart <rgb@ilm.com>
//---------------------------------------------------------------------------
//
// halfFunction<T> -- a class for fast evaluation
// of half --> T functions
//
// The constructor for a halfFunction object,
//
// halfFunction (function,
// domainMin, domainMax,
// defaultValue,
// posInfValue, negInfValue,
// nanValue);
//
// evaluates the function for all finite half values in the interval
// [domainMin, domainMax], and stores the results in a lookup table.
// For finite half values that are not in [domainMin, domainMax], the
// constructor stores defaultValue in the table. For positive infinity,
// negative infinity and NANs, posInfValue, negInfValue and nanValue
// are stored in the table.
//
// The tabulated function can then be evaluated quickly for arbitrary
// half values by calling the the halfFunction object's operator()
// method.
//
// Example:
//
// #include <math.h>
// #include <halfFunction.h>
//
// halfFunction<half> hsin (sin);
//
// halfFunction<half> hsqrt (sqrt, // function
// 0, HALF_MAX, // domain
// half::qNan(), // sqrt(x) for x < 0
// half::posInf(), // sqrt(+inf)
// half::qNan(), // sqrt(-inf)
// half::qNan()); // sqrt(nan)
//
// half x = hsin (1);
// half y = hsqrt (3.5);
//
//---------------------------------------------------------------------------
#ifndef _HALF_FUNCTION_H_
#define _HALF_FUNCTION_H_
#include "half.h"
#include "IlmBaseConfig.h"
#ifndef ILMBASE_HAVE_LARGE_STACK
#include <string.h> // need this for memset
#else
#endif
#include <float.h>
template <class T>
class halfFunction
{
public:
//------------
// Constructor
//------------
template <class Function>
halfFunction (Function f,
half domainMin = -HALF_MAX,
half domainMax = HALF_MAX,
T defaultValue = 0,
T posInfValue = 0,
T negInfValue = 0,
T nanValue = 0);
#ifndef ILMBASE_HAVE_LARGE_STACK
~halfFunction () { delete [] _lut; }
#endif
//-----------
// Evaluation
//-----------
T operator () (half x) const;
private:
#ifdef ILMBASE_HAVE_LARGE_STACK
T _lut[1 << 16];
#else
T * _lut;
#endif
};
//---------------
// Implementation
//---------------
template <class T>
template <class Function>
halfFunction<T>::halfFunction (Function f,
half domainMin,
half domainMax,
T defaultValue,
T posInfValue,
T negInfValue,
T nanValue)
{
#ifndef ILMBASE_HAVE_LARGE_STACK
_lut = new T[1<<16];
memset (_lut, 0 , (1<<16) * sizeof(T));
#endif
for (int i = 0; i < (1 << 16); i++)
{
half x;
x.setBits (i);
if (x.isNan())
_lut[i] = nanValue;
else if (x.isInfinity())
_lut[i] = x.isNegative()? negInfValue: posInfValue;
else if (x < domainMin || x > domainMax)
_lut[i] = defaultValue;
else
_lut[i] = f (x);
}
}
template <class T>
inline T
halfFunction<T>::operator () (half x) const
{
return _lut[x.bits()];
}
#endif
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