SinParameterTransformation.cxx

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// @(#)root/minuit2:$Id: SinParameterTransformation.cxx 28280 2009-04-20 14:08:59Z moneta $
// Authors: M. Winkler, F. James, L. Moneta, A. Zsenei   2003-2005  

/**********************************************************************
 *                                                                    *
 * Copyright (c) 2005 LCG ROOT Math team,  CERN/PH-SFT                *
 *                                                                    *
 **********************************************************************/

#include "Minuit2/SinParameterTransformation.h"
#include "Minuit2/MnMachinePrecision.h"

#include <math.h>

namespace ROOT {

   namespace Minuit2 {



double SinParameterTransformation::Int2ext(double Value, double Upper, double Lower) const {
   // transformation from  to internal (unlimited) to external values (limited by Lower/Upper )
   return Lower + 0.5*(Upper - Lower)*(sin(Value) + 1.);
}

double SinParameterTransformation::Ext2int(double Value, double Upper, double Lower, const MnMachinePrecision& prec) const {
   // transformation from external (limited by Lower/Upper )  to internal (unlimited) values given the lower/upper limits
   
   double piby2 = 2.*atan(1.);
   double distnn = 8.*sqrt(prec.Eps2());
   double vlimhi = piby2 - distnn;
   double vlimlo = -piby2 + distnn;
   
   double yy = 2.*(Value - Lower)/(Upper - Lower) - 1.;
   double yy2 = yy*yy;
   if(yy2 > (1. - prec.Eps2())) {
      if(yy < 0.) {
         // Lower limit
         //       std::cout<<"SinParameterTransformation warning: is at its Lower allowed limit. "<<Value<<std::endl;
         return vlimlo;
      } else {
         // Upper limit
         //       std::cout<<"SinParameterTransformation warning: is at its Upper allowed limit."<<std::endl;
         return vlimhi;
      }
      
   } else {
      return asin(yy); 
   }
}

double SinParameterTransformation::DInt2Ext(double Value, double Upper, double Lower) const {
   // return the derivative of the transformation d Ext/ d Int
   return 0.5*((Upper - Lower)*cos(Value));
}

   }  // namespace Minuit2

}  // namespace ROOT

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