SqrtLowParameterTransformation.cxx

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// @(#)root/minuit2:$Id$
// Authors: M. Winkler, F. James, L. Moneta, A. Zsenei, E.G.P. Bos   2003-2017
 
/**********************************************************************
 *                                                                    *
 * Copyright (c) 2005 LCG ROOT Math team,  CERN/PH-SFT                *
 *                                                                    *
 **********************************************************************/
 
// Project   : LCG
// Package   : Minuit
// Author    : Lorenzo.MONETA@cern.ch
// Created by: moneta  at Thu Apr  8 10:26:22 2004
 
#include "Minuit2/SqrtLowParameterTransformation.h"
#include "Minuit2/MnMachinePrecision.h"
 
namespace ROOT {
 
namespace Minuit2 {
 
long double SqrtLowParameterTransformation::Int2ext(long double value, long double lower) const
{
   /// internal to external transformation
   long double val = lower - 1. + std::sqrt(value * value + 1.);
   return val;
}
 
long double
SqrtLowParameterTransformation::Ext2int(long double value, long double lower, const MnMachinePrecision &) const
{
   // external to internal transformation
   long double yy = value - lower + 1.;
   long double yy2 = yy * yy;
   if (yy2 < 1.)
      return 0;
   else
      return std::sqrt(yy2 - 1);
}
 
long double SqrtLowParameterTransformation::DInt2Ext(long double value, long double) const
{
   // derivative of internal to external transformation   :  d (Int2Ext) / d Int
   long double val = value / (std::sqrt(value * value + 1.));
   return val;
}
 
long double SqrtLowParameterTransformation::DExt2Int(long double value, long double lower) const
{
   // derivative of internal to external transformation   :  d (Ext2Int) / d Ext
   long double val = (value - lower + 1) / (std::sqrt((value - lower + 1) * (value - lower + 1) - 1.));
   return val;
}
 
} // namespace Minuit2
 
} // namespace ROOT