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Reference Guide
MinimizerVariableTransformation.cxx
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1 // @(#)root/mathmore:$Id$
2 // Author: L. Moneta 2009
3 
4 // Implementation file for all the MinimizerVariableTransormation's
5 // (implementations taken from minuit2 classes)
6 
7 
9 #include <cmath>
10 #include <limits>
11 
12 namespace ROOT {
13 
14  namespace Math {
15 
16 // implementations for the class SinVariableTransformation
17 
18 double SinVariableTransformation::Int2ext(double value, double lower, double upper) const {
19  // transformation from internal (unlimited) to external values (limited by lower/upper )
20  return lower + 0.5*(upper - lower)*(std::sin(value) + 1.);
21 }
22 
23 double SinVariableTransformation::Ext2int(double value, double lower, double upper) const {
24  // transformation from external (limited by lower/upper ) to internal (unlimited) values given the lower/upper limits
25 
26  double piby2 = 2.*std::atan(1.);
27  static const double eps = std::numeric_limits<double>::epsilon();
28  double distnn = 8.*std::sqrt(eps);
29  double vlimhi = piby2 - distnn;
30  double vlimlo = -piby2 + distnn;
31 
32  double yy = 2.*(value - lower)/(upper - lower) - 1.;
33  double yy2 = yy*yy;
34  if(yy2 > (1. - 8 * eps) ) {
35  if(yy < 0.) {
36  // lower limit
37  // std::cout<<"SinVariableTransformation warning: is at its lower allowed limit. "<<value<<std::endl;
38  return vlimlo;
39  } else {
40  // upper limit
41  // std::cout<<"SinVariableTransformation warning: is at its upper allowed limit."<<std::endl;
42  return vlimhi;
43  }
44 
45  } else {
46  return std::asin(yy);
47  }
48 }
49 
50 double SinVariableTransformation::DInt2Ext(double value, double lower, double upper) const {
51  // return the derivative of the internal to external transformation (Int2Ext) : d Int2Ext / d Int
52  return 0.5*((upper - lower)*std::cos(value));
53 }
54 
55 // sqrt up
56 // implementations for the class SqrtUpVariableTransformation
57 
58 
59  double SqrtLowVariableTransformation::Int2ext(double value, double lower, double) const {
60  /// internal to external transformation
61  double val = lower - 1. + std::sqrt( value*value + 1.);
62  return val;
63 }
64 
65 
66 double SqrtLowVariableTransformation::Ext2int(double value, double lower, double ) const {
67  // external to internal transformation
68  double yy = value - lower + 1.;
69  double yy2 = yy*yy;
70  if (yy2 < 1. )
71  return 0;
72  else
73  return std::sqrt( yy2 -1);
74 }
75 
76 double SqrtLowVariableTransformation::DInt2Ext(double value, double, double) const {
77  // derivative of internal to external transofrmation : d (Int2Ext) / d Int
78  double val = value/( std::sqrt( value*value + 1.) );
79  return val;
80 }
81 
82 // sqrt up
83 // implementations for the class SqrtUpVariableTransformation
84 
85 double SqrtUpVariableTransformation::Int2ext(double value, double upper, double) const {
86  // internal to external transformation
87  double val = upper + 1. - std::sqrt( value*value + 1.);
88  return val;
89 }
90 
91 
92 double SqrtUpVariableTransformation::Ext2int(double value, double upper, double ) const {
93  // external to internal transformation
94  double yy = upper - value + 1.;
95  double arg = yy*yy - 1;
96  return ( arg < 0 ) ? 0 : std::sqrt(arg);
97 }
98 
99 
100 double SqrtUpVariableTransformation::DInt2Ext(double value, double, double) const {
101  // derivative of internal to external transofrmation : d Ext / d Int
102  double val = - value/( std::sqrt( value*value + 1.) );
103  return val;
104 }
105 
106 
107  } // end namespace Math
108 
109 } // end namespace ROOT
110 
VSD Structures.
Definition: StringConv.hxx:21
double cos(double)
double sqrt(double)
double Int2ext(double value, double lower, double upper) const
double Int2ext(double value, double lower, double upper) const
double sin(double)
double DInt2Ext(double value, double lower, double upper) const
double DInt2Ext(double value, double lower, double upper) const
double DInt2Ext(double value, double lower, double upper) const
double asin(double)
REAL epsilon
Definition: triangle.c:617
double Ext2int(double value, double lower, double upper) const
double atan(double)
double Ext2int(double value, double lower, double upper) const
Namespace for new Math classes and functions.
double Int2ext(double value, double lower, double upper) const
double Ext2int(double value, double lower, double upper) const