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/*
* Scilab ( http://www.scilab.org/ ) - This file is part of Scilab
* Copyright (C) 2007-2008 - INRIA - Bruno JOFRET
* Copyright (C) Bruno Pincon
*
* This file must be used under the terms of the CeCILL.
* This source file is licensed as described in the file COPYING, which
* you should have received as part of this distribution. The terms
* are also available at
* http://www.cecill.info/licences/Licence_CeCILL_V2-en.txt
*
*/
#include <math.h>
#include "log.h"
#include "lapack.h"
#include "log1p.h"
#include "pythag.h"
doubleComplex zlogs(doubleComplex in) {
static double sR2 = 1.41421356237309504;
double _RealIn = zreals(in);
double _ImgIn = zimags(in);
double _RealOut = 0;
double _ImgOut = 0;
double RMax = getOverflowThreshold();
double LInf = sqrt(getUnderflowThreshold());
double LSup = sqrt(0.5 * RMax);
double AbsReal = fabs(_RealIn);
double AbsImg = fabs(_ImgIn);
_ImgOut = atan2(_ImgIn, _RealIn);
if(_ImgIn > _RealIn)
{/* switch Real part and Imaginary part */
double Temp = AbsReal;
AbsReal = AbsImg;
AbsImg = Temp;
}
if((0.5 <= AbsReal) && (AbsReal <= sR2))
_RealOut = 0.5 * dlog1ps((AbsReal - 1) * (AbsReal + 1) + AbsImg * AbsImg);
else if(LInf < AbsImg && AbsReal < LSup)
_RealOut = 0.5 * dlogs(AbsReal * AbsReal + AbsImg * AbsImg);
else if(AbsReal > RMax)
_RealOut = AbsReal;
else
{
double Temp = dpythags(AbsReal, AbsImg);
if(Temp <= RMax)
{
_RealOut = dlogs(Temp);
}
else /* handle rare spurious overflow with : */
{
double Temp2 = AbsImg/AbsReal;
_RealOut = dlogs(AbsReal) + 0.5 * dlog1ps(Temp2 * Temp2);
}
}
return DoubleComplex(_RealOut, _ImgOut);
}
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