Stan Math Library  2.11.0
reverse mode automatic differentiation
fdim.hpp
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1 #ifndef STAN_MATH_REV_SCAL_FUN_FDIM_HPP
2 #define STAN_MATH_REV_SCAL_FUN_FDIM_HPP
3 
4 #include <stan/math/rev/core.hpp>
5 #include <boost/math/special_functions/fpclassify.hpp>
7 #include <limits>
8 
9 namespace stan {
10  namespace math {
11 
12  namespace {
13  class fdim_vv_vari : public op_vv_vari {
14  public:
15  fdim_vv_vari(vari* avi, vari* bvi) :
16  op_vv_vari(avi->val_ - bvi->val_, avi, bvi) {
17  }
18  void chain() {
19  if (unlikely(boost::math::isnan(avi_->val_)
20  || boost::math::isnan(bvi_->val_))) {
21  avi_->adj_ = std::numeric_limits<double>::quiet_NaN();
22  bvi_->adj_ = std::numeric_limits<double>::quiet_NaN();
23  } else {
24  avi_->adj_ += adj_;
25  bvi_->adj_ -= adj_;
26  }
27  }
28  };
29 
30  class fdim_vd_vari : public op_vd_vari {
31  public:
32  fdim_vd_vari(vari* avi, double b) :
33  op_vd_vari(avi->val_ - b, avi, b) {
34  }
35  void chain() {
36  if (unlikely(boost::math::isnan(avi_->val_)
37  || boost::math::isnan(bd_)))
38  avi_->adj_ = std::numeric_limits<double>::quiet_NaN();
39  else
40  avi_->adj_ += adj_;
41  }
42  };
43 
44  class fdim_dv_vari : public op_dv_vari {
45  public:
46  fdim_dv_vari(double a, vari* bvi) :
47  op_dv_vari(a - bvi->val_, a, bvi) {
48  }
49  void chain() {
50  if (unlikely(boost::math::isnan(bvi_->val_)
51  || boost::math::isnan(ad_)))
52  bvi_->adj_ = std::numeric_limits<double>::quiet_NaN();
53  else
54  bvi_->adj_ -= adj_;
55  }
56  };
57  }
58 
110  inline var fdim(const stan::math::var& a,
111  const stan::math::var& b) {
112  if (!(a.vi_->val_ <= b.vi_->val_))
113  return var(new fdim_vv_vari(a.vi_, b.vi_));
114  else
115  return var(new vari(0.0));
116  }
117 
135  inline var fdim(const double& a,
136  const stan::math::var& b) {
137  return a <= b.vi_->val_
138  ? var(new vari(0.0))
139  : var(new fdim_dv_vari(a, b.vi_));
140  }
141 
158  inline var fdim(const stan::math::var& a,
159  const double& b) {
160  return a.vi_->val_ <= b
161  ? var(new vari(0.0))
162  : var(new fdim_vd_vari(a.vi_, b));
163  }
164 
165  }
166 }
167 #endif
The variable implementation base class.
Definition: vari.hpp:30
Independent (input) and dependent (output) variables for gradients.
Definition: var.hpp:31
const double val_
The value of this variable.
Definition: vari.hpp:38
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
fvar< T > fdim(const fvar< T > &x1, const fvar< T > &x2)
Definition: fdim.hpp:11
vari * vi_
Pointer to the implementation of this variable.
Definition: var.hpp:43

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