Stan Math Library  2.10.0
reverse mode automatic differentiation
F32.hpp
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1 #ifndef STAN_MATH_PRIM_SCAL_FUN_F32_HPP
2 #define STAN_MATH_PRIM_SCAL_FUN_F32_HPP
3 
4 #include <cmath>
5 
6 namespace stan {
7 
8  namespace math {
9 
10  template<typename T>
11  T F32(T a, T b, T c, T d, T e, T z, T precision = 1e-6) {
12  using std::exp;
13  using std::log;
14  using std::fabs;
15 
16  T F = 1.0;
17 
18  T tNew = 0.0;
19 
20  T logT = 0.0;
21 
22  T logZ = log(z);
23 
24  int k = 0.0;
25 
26  while (fabs(tNew) > precision || k == 0) {
27  T p = (a + k) * (b + k) * (c + k) / ( (d + k) * (e + k) * (k + 1) );
28 
29  // If a, b, or c is a negative integer then the series terminates
30  // after a finite number of interations
31  if (p == 0) break;
32 
33  logT += (p > 0 ? 1.0 : -1.0) * log(fabs(p)) + logZ;
34 
35  tNew = exp(logT);
36 
37  F += tNew;
38 
39  ++k;
40  }
41  return F;
42  }
43 
44  }
45 }
46 #endif
fvar< T > fabs(const fvar< T > &x)
Definition: fabs.hpp:14
fvar< T > log(const fvar< T > &x)
Definition: log.hpp:15
fvar< T > exp(const fvar< T > &x)
Definition: exp.hpp:10
double e()
Return the base of the natural logarithm.
Definition: constants.hpp:95
T F32(T a, T b, T c, T d, T e, T z, T precision=1e-6)
Definition: F32.hpp:11

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