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authorSiddhesh Wani2015-05-25 14:46:31 +0530
committerSiddhesh Wani2015-05-25 14:46:31 +0530
commitdb464f35f5a10b58d9ed1085e0b462689adee583 (patch)
treede5cdbc71a54765d9fec33414630ae2c8904c9b8 /src/c/elementaryFunctions/log/zlogs.c
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Original Version
Diffstat (limited to 'src/c/elementaryFunctions/log/zlogs.c')
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diff --git a/src/c/elementaryFunctions/log/zlogs.c b/src/c/elementaryFunctions/log/zlogs.c
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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);
+}