Stan Math Library  2.6.3
probability, sampling & optimization
 All Classes Namespaces Files Functions Variables Typedefs Enumerator Friends Macros
log_falling_factorial.hpp
Go to the documentation of this file.
1 #ifndef STAN_MATH_REV_SCAL_FUN_LOG_FALLING_FACTORIAL_HPP
2 #define STAN_MATH_REV_SCAL_FUN_LOG_FALLING_FACTORIAL_HPP
3 
4 #include <stan/math/rev/core.hpp>
6 #include <boost/math/special_functions/digamma.hpp>
7 #include <boost/math/special_functions/fpclassify.hpp>
8 #include <limits>
9 
10 namespace stan {
11  namespace math {
12 
13  namespace {
14 
15  class log_falling_factorial_vv_vari : public op_vv_vari {
16  public:
17  log_falling_factorial_vv_vari(vari* avi, vari* bvi) :
18  op_vv_vari(stan::math::log_falling_factorial(avi->val_, bvi->val_),
19  avi, bvi) {
20  }
21  void chain() {
22  if (unlikely(boost::math::isnan(avi_->val_)
23  || boost::math::isnan(bvi_->val_))) {
24  avi_->adj_ = std::numeric_limits<double>::quiet_NaN();
25  bvi_->adj_ = std::numeric_limits<double>::quiet_NaN();
26  } else {
27  avi_->adj_ += adj_ * boost::math::digamma(avi_->val_ + 1);
28  bvi_->adj_ += adj_ * -boost::math::digamma(bvi_->val_ + 1);
29  }
30  }
31  };
32 
33  class log_falling_factorial_vd_vari : public op_vd_vari {
34  public:
35  log_falling_factorial_vd_vari(vari* avi, double b) :
36  op_vd_vari(stan::math::log_falling_factorial(avi->val_, b), avi, b) {
37  }
38  void chain() {
39  if (unlikely(boost::math::isnan(avi_->val_)
40  || boost::math::isnan(bd_)))
41  avi_->adj_ = std::numeric_limits<double>::quiet_NaN();
42  else
43  avi_->adj_ += adj_ * boost::math::digamma(avi_->val_ + 1);
44  }
45  };
46 
47  class log_falling_factorial_dv_vari : public op_dv_vari {
48  public:
49  log_falling_factorial_dv_vari(double a, vari* bvi) :
50  op_dv_vari(stan::math::log_falling_factorial(a, bvi->val_), a, bvi) {
51  }
52  void chain() {
54  || boost::math::isnan(bvi_->val_)))
55  bvi_->adj_ = std::numeric_limits<double>::quiet_NaN();
56  else
57  bvi_->adj_ += adj_ * -boost::math::digamma(bvi_->val_ + 1);
58  }
59  };
60  }
61 
62  inline var log_falling_factorial(const var& a,
63  const double& b) {
64  return var(new log_falling_factorial_vd_vari(a.vi_, b));
65  }
66 
67  inline var log_falling_factorial(const var& a,
68  const var& b) {
69  return var(new log_falling_factorial_vv_vari(a.vi_, b.vi_));
70  }
71 
72  inline var log_falling_factorial(const double& a,
73  const var& b) {
74  return var(new log_falling_factorial_dv_vari(a, b.vi_));
75  }
76  }
77 }
78 #endif
fvar< T > log_falling_factorial(const fvar< T > &x, const fvar< T > &n)
Independent (input) and dependent (output) variables for gradients.
Definition: var.hpp:32
bool isnan(const stan::math::var &v)
Checks if the given number is NaN.
Definition: boost_isnan.hpp:22
#define unlikely(x)
Definition: likely.hpp:9
vari * vi_
Pointer to the implementation of this variable.
Definition: var.hpp:44
fvar< T > digamma(const fvar< T > &x)
Definition: digamma.hpp:16

     [ Stan Home Page ] © 2011–2015, Stan Development Team.