source: trunk/source/global/management/include/G4Pow.hh @ 1315

Last change on this file since 1315 was 1315, checked in by garnier, 14 years ago

update geant4-09-04-beta-cand-01 interfaces-V09-03-09 vis-V09-03-08

File size: 4.7 KB
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25//
26// $Id: G4Pow.hh,v 1.5 2010/05/28 08:18:03 vnivanch Exp $
27// GEANT4 tag $Name: geant4-09-04-beta-cand-01 $
28//
29//
30// -------------------------------------------------------------------
31//
32// Class G4Pow
33//
34// Class description:
35//
36// Utility singleton class for the fast computation of log and pow
37// functions. Integer argument should in the interval 0-255, no
38// check is performed inside these methods for performance reasons.
39// Computations with double arguments are fast for the interval
40// 0.5-255.5, standard library is used in the opposite case
41
42// Author: Vladimir Ivanchenko
43//
44// Creation date: 23.05.2009
45// -------------------------------------------------------------------
46
47#ifndef G4Pow_h
48#define G4Pow_h 1
49
50#include "globals.hh"
51#include "G4DataVector.hh"
52
53class G4Pow
54{
55
56  public:
57
58    static G4Pow* GetInstance();
59
60    // Fast computation of Z^1/3
61    //
62    inline G4double Z13(G4int Z);
63    inline G4double A13(G4double A);
64
65    // Fast computation of Z^2/3
66    //
67    inline G4double Z23(G4int Z);
68    inline G4double A23(G4double A);
69
70    // Fast computation of log(Z)
71    //
72    inline G4double logZ(G4int Z);
73    inline G4double logA(G4double A);
74
75    // Fast computation of log10(Z)
76    //
77    inline G4double log10Z(G4int Z);
78    inline G4double log10A(G4double A);
79
80    // Fast computation of pow(Z,X)
81    //
82    inline G4double powZ(G4int Z, G4double y);
83    inline G4double powA(G4double A, G4double y);
84
85    // Fast factorial
86    //
87    inline G4double factorial(G4int Z);
88
89  private:
90
91    G4Pow();
92   ~G4Pow();
93
94  private:
95
96    static G4Pow* fInstance;
97
98    G4double onethird;
99
100    G4DataVector pz13;
101    G4DataVector lz;
102    G4DataVector fact;
103};
104
105// -------------------------------------------------------------------
106
107inline G4double G4Pow::Z13(G4int Z)
108{
109  return pz13[Z];
110}
111
112inline G4double G4Pow::A13(G4double A)
113{
114  const G4double minA = 0.5000001; 
115  const G4double maxA = 255.5; 
116
117  G4double res;
118  if((A >= minA) && (A <= maxA))
119  {
120    G4int i = G4int(A + 0.5);
121    G4double x = (1.0 - A/G4double(i))*onethird;
122    res = pz13[i]*(1.0 + x - x*x*(1.0 - 1.66666666*x));
123  }
124  else
125  {
126    res = std::pow(A, onethird); 
127  }
128  return res;
129}
130
131inline G4double G4Pow::Z23(G4int Z)
132{
133  G4double x = Z13(Z);
134  return x*x;
135}
136
137inline G4double G4Pow::A23(G4double A)
138{
139  G4double x = A13(A);
140  return x*x;
141}
142
143inline G4double G4Pow::logZ(G4int Z)
144{
145  return lz[Z];
146}
147
148inline G4double G4Pow::logA(G4double A)
149{
150  const G4double minA = 0.5000001; 
151  const G4double maxA = 255.5; 
152
153  G4double res;
154  if((A >= minA) && (A <= maxA))
155  {
156    G4int i = G4int(A + 0.5);
157    G4double x = 1.0 - A/G4double(i);
158    res = lz[i] + x*(1.0 - 0.5*x + onethird*x*x);
159  }
160  else
161  {
162    res = std::log(A);
163  }
164  return res;
165}
166
167inline G4double G4Pow::log10Z(G4int Z)
168{
169  return lz[Z]/lz[10];
170}
171
172inline G4double G4Pow::log10A(G4double A)
173{
174  return logA(A)/lz[10];
175}
176
177inline G4double G4Pow::powZ(G4int Z, G4double y)
178{
179  return std::exp(y*lz[Z]);
180}
181
182inline G4double G4Pow::powA(G4double A, G4double y)
183{
184  return std::exp(y*logA(A));
185}
186
187inline G4double G4Pow::factorial(G4int Z)
188{
189  return fact[Z];
190}
191
192// -------------------------------------------------------------------
193
194#endif
195
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