Stan Math Library  2.11.0
reverse mode automatic differentiation
atan2.hpp
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1 #ifndef STAN_MATH_REV_SCAL_FUN_ATAN2_HPP
2 #define STAN_MATH_REV_SCAL_FUN_ATAN2_HPP
3 
4 #include <stan/math/rev/core.hpp>
5 #include <cmath>
6 #include <valarray>
7 
8 namespace stan {
9  namespace math {
10 
11  namespace {
12  class atan2_vv_vari : public op_vv_vari {
13  public:
14  atan2_vv_vari(vari* avi, vari* bvi) :
15  op_vv_vari(std::atan2(avi->val_, bvi->val_), avi, bvi) {
16  }
17  void chain() {
18  double a_sq_plus_b_sq = (avi_->val_ * avi_->val_)
19  + (bvi_->val_ * bvi_->val_);
20  avi_->adj_ += adj_ * bvi_->val_ / a_sq_plus_b_sq;
21  bvi_->adj_ -= adj_ * avi_->val_ / a_sq_plus_b_sq;
22  }
23  };
24 
25  class atan2_vd_vari : public op_vd_vari {
26  public:
27  atan2_vd_vari(vari* avi, double b) :
28  op_vd_vari(std::atan2(avi->val_, b), avi, b) {
29  }
30  void chain() {
31  double a_sq_plus_b_sq = (avi_->val_ * avi_->val_) + (bd_ * bd_);
32  avi_->adj_ += adj_ * bd_ / a_sq_plus_b_sq;
33  }
34  };
35 
36  class atan2_dv_vari : public op_dv_vari {
37  public:
38  atan2_dv_vari(double a, vari* bvi) :
39  op_dv_vari(std::atan2(a, bvi->val_), a, bvi) {
40  }
41  void chain() {
42  double a_sq_plus_b_sq = (ad_ * ad_) + (bvi_->val_ * bvi_->val_);
43  bvi_->adj_ -= adj_ * ad_ / a_sq_plus_b_sq;
44  }
45  };
46  }
47 
62  inline var atan2(const var& a, const var& b) {
63  return var(new atan2_vv_vari(a.vi_, b.vi_));
64  }
65 
78  inline var atan2(const var& a, const double b) {
79  return var(new atan2_vd_vari(a.vi_, b));
80  }
81 
119  inline var atan2(const double a, const var& b) {
120  return var(new atan2_dv_vari(a, b.vi_));
121  }
122 
123  }
124 }
125 #endif
fvar< T > atan2(const fvar< T > &x1, const fvar< T > &x2)
Definition: atan2.hpp:12
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

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