Stan Math Library  2.9.0
reverse mode automatic differentiation
rising_factorial.hpp
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1 #ifndef STAN_MATH_REV_SCAL_FUN_RISING_FACTORIAL_HPP
2 #define STAN_MATH_REV_SCAL_FUN_RISING_FACTORIAL_HPP
3 
4 #include <stan/math/rev/core.hpp>
6 #include <boost/math/special_functions/digamma.hpp>
7 
8 namespace stan {
9  namespace math {
10 
11  namespace {
12 
13  class rising_factorial_vv_vari : public op_vv_vari {
14  public:
15  rising_factorial_vv_vari(vari* avi, vari* bvi) :
16  op_vv_vari(stan::math::rising_factorial(avi->val_, bvi->val_),
17  avi, bvi) {
18  }
19  void chain() {
20  avi_->adj_ += adj_
21  * stan::math::rising_factorial(avi_->val_, bvi_->val_)
22  * (boost::math::digamma(avi_->val_ + bvi_->val_)
23  - boost::math::digamma(avi_->val_));
24  bvi_->adj_ += adj_
25  * stan::math::rising_factorial(avi_->val_, bvi_->val_)
26  * boost::math::digamma(bvi_->val_ + avi_->val_);
27  }
28  };
29 
30  class rising_factorial_vd_vari : public op_vd_vari {
31  public:
32  rising_factorial_vd_vari(vari* avi, double b) :
33  op_vd_vari(stan::math::rising_factorial(avi->val_, b), avi, b) {
34  }
35  void chain() {
36  avi_->adj_ += adj_ * stan::math::rising_factorial(avi_->val_, bd_)
37  * (boost::math::digamma(avi_->val_ + bd_)
38  - boost::math::digamma(avi_->val_));
39  }
40  };
41 
42  class rising_factorial_dv_vari : public op_dv_vari {
43  public:
44  rising_factorial_dv_vari(double a, vari* bvi) :
45  op_dv_vari(stan::math::rising_factorial(a, bvi->val_), a, bvi) {
46  }
47  void chain() {
48  bvi_->adj_ += adj_ * stan::math::rising_factorial(ad_, bvi_->val_)
49  * boost::math::digamma(bvi_->val_ + ad_);
50  }
51  };
52  }
53 
54  inline var rising_factorial(const var& a,
55  const double& b) {
56  return var(new rising_factorial_vd_vari(a.vi_, b));
57  }
58 
59  inline var rising_factorial(const var& a,
60  const var& b) {
61  return var(new rising_factorial_vv_vari(a.vi_, b.vi_));
62  }
63 
64  inline var rising_factorial(const double& a,
65  const var& b) {
66  return var(new rising_factorial_dv_vari(a, b.vi_));
67  }
68  }
69 }
70 #endif
Independent (input) and dependent (output) variables for gradients.
Definition: var.hpp:31
vari * vi_
Pointer to the implementation of this variable.
Definition: var.hpp:43
fvar< T > rising_factorial(const fvar< T > &x, const fvar< T > &n)
fvar< T > digamma(const fvar< T > &x)
Definition: digamma.hpp:16

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