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reverse mode automatic differentiation
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lbeta.hpp
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1 #ifndef STAN_MATH_FWD_SCAL_FUN_LBETA_HPP
2 #define STAN_MATH_FWD_SCAL_FUN_LBETA_HPP
3 
4 #include <stan/math/fwd/core.hpp>
5 
6 #include <boost/math/special_functions/digamma.hpp>
8 
9 namespace stan {
10 
11  namespace math {
12 
13  template <typename T>
14  inline
15  fvar<T>
16  lbeta(const fvar<T>& x1, const fvar<T>& x2) {
17  using stan::math::lbeta;
19  return fvar<T>(lbeta(x1.val_, x2.val_),
20  x1.d_ * digamma(x1.val_)
21  + x2.d_ * digamma(x2.val_)
22  - (x1.d_ + x2.d_) * digamma(x1.val_ + x2.val_));
23  }
24 
25  template <typename T>
26  inline
27  fvar<T>
28  lbeta(const double x1, const fvar<T>& x2) {
29  using stan::math::lbeta;
31  return fvar<T>(lbeta(x1, x2.val_),
32  x2.d_ * digamma(x2.val_) - x2.d_ * digamma(x1 + x2.val_));
33  }
34 
35  template <typename T>
36  inline
37  fvar<T>
38  lbeta(const fvar<T>& x1, const double x2) {
39  using stan::math::lbeta;
41  return fvar<T>(lbeta(x1.val_, x2),
42  x1.d_ * digamma(x1.val_) - x1.d_ * digamma(x1.val_ + x2));
43  }
44  }
45 }
46 #endif
fvar< T > lbeta(const fvar< T > &x1, const fvar< T > &x2)
Definition: lbeta.hpp:16
fvar< T > digamma(const fvar< T > &x)
Definition: digamma.hpp:16

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