FastJet  3.2.0
inline_maths.h
1 #ifndef INLINE_MATHS
2 #define INLINE_MATHS
3 
4 // This file is distributed with FastJet under the terms of the GNU
5 // General Public License (v2). Permission to do so has been granted
6 // by Lars Sonnenschein and the D0 collaboration (see COPYING for
7 // details)
8 //
9 // History of changes in FastJet compared tothe original version of
10 // inline_math.h
11 //
12 // 2011-12-13 Gregory Soyez <soyez@fastjet.fr>
13 //
14 // * added license information
15 //
16 // 2011-10-06 Gregory Soyez <soyez@fastjet.fr>
17 //
18 // * put the code in the fastjet::d0runi namespace
19 
20 #include <cmath>
21 #include <cerrno>
22 #include <fastjet/internal/base.hh>
23 
24 FASTJET_BEGIN_NAMESPACE
25 
26 //using namespace std;
27 
28 namespace d0runi{
29 namespace inline_maths {
30 
31 const double PI = fabs(acos(-1.));
32 
33 const double TWOPI = 2*PI;
34 
35 
36 inline double sqr(double a) {
37  return a*a;
38 }
39 
40 
41 
42 inline double min(double a, double b) {
43  return (a < b) ? a : b;
44 }
45 
46 
47 
48 inline double delta_phi(double phi1, double phi2) {
49  double dphi = min( double(fabs(phi1-phi2)), double(2.*PI-fabs(phi1-phi2)) );
50  return (phi1 < phi2) ? -dphi : dphi;
51 }
52 
53 
54 
55 inline double phi(double px, double py) {
56  return atan2(py, px);
57 }
58 
59 
60 
61 inline double y(double E, double pz) {
62  errno=0;
63  double y;
64  //cout << "inline_maths: ";
65  if (fabs(E-pz) == 0.) {
66  // cout << "Error in header mathe.h: division by 0 in function y!" << " p=" << p << " pz=" << pz << endl;
67  // exit(721);
68  errno=721;
69  y = 99999.;
70  }
71  else {
72  y = 0.5*log((E+pz)/(E-pz));
73  }
74  //cout << "y: E=" << E << " pz=" << pz << " y=" << y << endl;
75  return y;
76 }
77 
78 
79 
80 
81 inline double eta(double p, double pz) {
82  errno=0;
83  double eta;
84  //cout << "inline_maths: ";
85  if (fabs(p-pz) == 0.) {
86  // cout << "Error in header mathe.h: division by 0 in function eta!" << " p=" << p << " pz=" << pz << endl;
87  // exit(721);
88  errno=721;
89  eta = 99999.;
90  }
91  else {
92  eta = 0.5*log((p+pz)/(p-pz));
93  }
94  //cout << "eta: p=" << p << " pz=" << pz << " eta=" << eta << endl;
95  return eta;
96 }
97 
98 
99 
100 
101  inline double eta(double px, double py, double pz) {
102  errno=0;
103  double eta;
104  //cout << "inline_maths: ";
105  double p = sqrt(px*px+py*py+pz*pz);
106  if (fabs(p-pz) == 0.) {
107  // cout << "Error in header mathe.h: division by 0 in function eta!" << " p=" << p << " pz=" << pz << endl;
108  // exit(721);
109  errno=721;
110  eta = 99999.;
111  }
112  else {
113  eta = 0.5*log((p+pz)/(p-pz));
114  }
115  //cout << "eta: p=" << p << " pz=" << pz << " eta=" << eta << endl;
116  return eta;
117 }
118 
119 
120 
121  inline double eta(double theta) {
122  double eta = -log(tan(theta/2.));
123 
124  return eta;
125  }
126 
127 
128  inline double theta(double eta) {
129  double theta = 2.*atan(exp(-eta));
130 
131  return theta;
132  }
133 
134  inline double theta(double px, double py, double pz) {
135  double Eta = eta(px, py, pz);
136  double theta = 2.*atan(exp(-Eta));
137 
138  return theta;
139  }
140 
141 
142 
143 } //end usename inline_maths
144 } //end usename d0runi
145 
146 FASTJET_END_NAMESPACE
147 
148 
149 #endif