Add Scilab algorithm emulation

1 files changed, 140 insertions, 12 deletions

diff --git a/src/elementaryFunctions/acos/cacoss.c b/src/elementaryFunctions/acos/cacoss.c
index ed174fda..1059c8c3 100644
--- a/src/elementaryFunctions/acos/cacoss.c
+++ b/src/elementaryFunctions/acos/cacoss.c
@@ -1,18 +1,146 @@
 /*
-**  -*- C -*-
-**
-** cacoss.c
-** Made by  Bruno JOFRET <bruno.jofret@inria.fr>
-**
-** Started on  Fri Jan  5 11:29:45 2007 jofret
-** Last update Fri Feb 23 16:37:08 2007 jofret
-**
-** Copyright INRIA 2007
-*/
+ *  Scilab ( http://www.scilab.org/ ) - This file is part of Scilab
+ *  Copyright (C) 2007-2008 - INRIA - Bruno JOFRET
+ *
+ *  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
+ *
+ */
+
+/*
+ * This fonction is a translation of fortran wacos write by Bruno Pincon <Bruno.Pincon@iecn.u-nancy.fr>
+ *     REFERENCE
+ *        This is a Fortran-77 translation of an algorithm by
+ *        T.E. Hull, T. F. Fairgrieve and P.T.P. Tang which
+ *        appears in their article :
+ *          "Implementing the Complex Arcsine and Arccosine
+ *           Functions Using Exception Handling", ACM, TOMS,
+ *           Vol 23, No. 3, Sept 1997, p. 299-335
+ */
 
 #include "acos.h"
+#include "atan.h"
+#include "log.h"
+#include "log1p.h"
+#include "sqrt.h"
+#include "abs.h"
+#include "lapack.h"
+#include "min.h"
+#include "max.h"
+
+#define localSign(x) (x>0 ? 1.0f : -1.0f)
 
 floatComplex		cacoss(floatComplex z) {
-  /* FIXME: Dummy... */
-  return z;
+	static float sfltPi		= 3.1415926535897932384626433f;
+	static float sfltPi_2		= 1.5707963267948966192313216f;
+	static float sfltLn2		= 0.6931471805599453094172321f;
+	static float sfltAcross	= 1.5f;
+	static float sfltBcross	= 0.6417f;
+
+	float fltLsup = ssqrts((float) getOverflowThreshold())/8.0f;
+	float fltLinf = 4.0f * ssqrts((float) getUnderflowThreshold());
+	float fltEpsm = ssqrts((float) getRelativeMachinePrecision());
+
+	float fltAbsReal	= sabss(creals(z));
+	float fltAbsImg		= sabss(cimags(z));
+	float fltSignReal	= localSign(creals(z));
+	float fltSignImg	= localSign(cimags(z));
+
+	float fltR = 0, fltS = 0, fltA = 0, fltB = 0;
+
+	float fltTemp = 0;
+
+	float _pfltReal = 0;
+	float _pfltImg = 0;
+
+	if( min(fltAbsReal, fltAbsImg) > fltLinf && max(fltAbsReal, fltAbsImg) <= fltLsup)
+	  {/* we are in the safe region */
+		fltR = ssqrts( (fltAbsReal + 1 )*(fltAbsReal + 1 ) + fltAbsImg*fltAbsImg);
+		fltS = ssqrts( (fltAbsReal - 1 )*(fltAbsReal - 1 ) + fltAbsImg*fltAbsImg);
+		fltA = 0.5f * ( fltR + fltS );
+		fltB = fltAbsReal / fltA;
+
+
+		/* compute the real part */
+		if(fltB <= sfltBcross)
+			_pfltReal = sacoss(fltB);
+		else if( fltAbsReal <= 1)
+			_pfltReal = satans(ssqrts(0.5f * (fltA + fltAbsReal) * (fltAbsImg*fltAbsImg / (fltR + (fltAbsReal + 1)) + (fltS + (1 - fltAbsReal)))) / fltAbsReal);
+		else
+			_pfltReal = satans((fltAbsImg * ssqrts(0.5f * ((fltA + fltAbsReal) / (fltR + (fltAbsReal + 1)) + (fltA + fltAbsReal) / (fltS + (fltAbsReal - 1))))) / fltAbsReal);
+
+		/* compute the imaginary part */
+		if(fltA <= sfltAcross)
+		{
+			float fltImg1 = 0;
+
+			if(fltAbsReal < 1)
+			  /* Am1 = 0.5d0*((y**2)/(R+(x+1.d0))+(y**2)/(S+(1.d0-x))) */
+				fltImg1 = 0.5f * (fltAbsImg*fltAbsImg / (fltR + (fltAbsReal + 1)) + fltAbsImg*fltAbsImg / (fltS + (1 - fltAbsReal)));
+			else
+			  /* Am1 = 0.5d0*((y**2)/(R+(x+1.d0))+(S+(x-1.d0))) */
+				fltImg1 = 0.5f * (fltAbsImg*fltAbsImg / (fltR + (fltAbsReal + 1)) + (fltS + (fltAbsReal - 1)));
+			/* ai = logp1(Am1 + sqrt(Am1*(A+1.d0))) */
+			fltTemp = fltImg1 + ssqrts(fltImg1 *( fltA + 1));
+			_pfltImg = slog1ps(fltTemp);
+		}
+		else
+		  /* ai = log(A + sqrt(A**2 - 1.d0)) */
+			_pfltImg = slogs(fltA + ssqrts(fltA*fltA - 1));
+	}
+	else
+	  {/* evaluation in the special regions ... */
+		if(fltAbsImg <= fltEpsm * sabss(fltAbsReal - 1))
+		{
+			if(fltAbsReal < 1)
+			{
+				_pfltReal	= sacoss(fltAbsReal);
+				_pfltImg	= fltAbsImg / ssqrts((1 + fltAbsReal) * (1 - fltAbsReal));
+			}
+			else
+			{
+				_pfltReal = 0;
+				if(fltAbsReal <= fltLsup)
+				{
+					fltTemp		= (fltAbsReal - 1) + ssqrts((fltAbsReal - 1) * (fltAbsReal + 1));
+					_pfltImg	= slog1ps(fltTemp);
+				}
+				else
+					_pfltImg	= sfltLn2 + slogs(fltAbsReal);
+			}
+		}
+		else if(fltAbsImg < fltLinf)
+		{
+			_pfltReal	= ssqrts(fltAbsImg);
+			_pfltImg	= _pfltReal;
+		}
+		else if((fltEpsm * fltAbsImg - 1 >= fltAbsReal))
+		{
+			_pfltReal	= sfltPi_2;
+			_pfltImg	= sfltLn2 + slogs(fltAbsImg);
+		}
+		else if(fltAbsReal > 1)
+		{
+			_pfltReal	= satans(fltAbsImg / fltAbsReal);
+			fltTemp		= (fltAbsReal / fltAbsImg)*(fltAbsReal / fltAbsImg);
+			_pfltImg	= sfltLn2 + slogs(fltAbsImg) + 0.5f * slog1ps(fltTemp);
+		}
+		else
+		{
+			float fltTemp2 = ssqrts(1 + fltAbsImg*fltAbsImg);
+			_pfltReal	= sfltPi_2;
+			fltTemp		= 2 * fltAbsImg * (fltAbsImg + fltTemp2);
+			_pfltImg	= 0.5f * slog1ps(fltTemp);
+		}
+	}
+	if(fltSignReal < 0)
+		_pfltReal = sfltPi - _pfltReal;
+
+	if(fltAbsImg != 0 || fltSignReal < 0)
+		_pfltImg = - fltSignImg * _pfltImg;
+
+	return FloatComplex(_pfltReal, _pfltImg);
 }