Stan Math Library  2.20.0
reverse mode automatic differentiation
atan.hpp
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1 #ifndef STAN_MATH_REV_SCAL_FUN_ATAN_HPP
2 #define STAN_MATH_REV_SCAL_FUN_ATAN_HPP
3 
4 #include <stan/math/rev/meta.hpp>
5 #include <stan/math/rev/core.hpp>
6 #include <cmath>
7 
8 namespace stan {
9 namespace math {
10 
11 namespace internal {
12 class atan_vari : public op_v_vari {
13  public:
14  explicit atan_vari(vari* avi) : op_v_vari(std::atan(avi->val_), avi) {}
15  void chain() { avi_->adj_ += adj_ / (1.0 + (avi_->val_ * avi_->val_)); }
16 };
17 } // namespace internal
18 
49 inline var atan(const var& a) { return var(new internal::atan_vari(a.vi_)); }
50 
51 } // namespace math
52 } // namespace stan
53 #endif
The variable implementation base class.
Definition: vari.hpp:30
void chain()
Apply the chain rule to this variable based on the variables on which it depends. ...
Definition: atan.hpp:15
Independent (input) and dependent (output) variables for gradients.
Definition: var.hpp:33
fvar< T > atan(const fvar< T > &x)
Definition: atan.hpp:13
friend class var
Definition: vari.hpp:32
const double val_
The value of this variable.
Definition: vari.hpp:38
vari * vi_
Pointer to the implementation of this variable.
Definition: var.hpp:45
double adj_
The adjoint of this variable, which is the partial derivative of this variable with respect to the ro...
Definition: vari.hpp:44

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