Stan Math Library  2.20.0
reverse mode automatic differentiation
Phi.hpp
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1 #ifndef STAN_MATH_REV_SCAL_FUN_PHI_HPP
2 #define STAN_MATH_REV_SCAL_FUN_PHI_HPP
3 
4 #include <stan/math/rev/meta.hpp>
5 #include <stan/math/rev/core.hpp>
7 
8 namespace stan {
9 namespace math {
10 
11 namespace internal {
12 class Phi_vari : public op_v_vari {
13  public:
14  explicit Phi_vari(vari* avi) : op_v_vari(Phi(avi->val_), avi) {}
15  void chain() {
16  static const double NEG_HALF = -0.5;
18  * std::exp(NEG_HALF * avi_->val_ * avi_->val_);
19  }
20 };
21 } // namespace internal
22 
64 inline var Phi(const var& a) { return var(new internal::Phi_vari(a.vi_)); }
65 
66 } // namespace math
67 } // namespace stan
68 #endif
const double INV_SQRT_TWO_PI
Definition: constants.hpp:142
The variable implementation base class.
Definition: vari.hpp:30
Independent (input) and dependent (output) variables for gradients.
Definition: var.hpp:33
friend class var
Definition: vari.hpp:32
const double val_
The value of this variable.
Definition: vari.hpp:38
void chain()
Apply the chain rule to this variable based on the variables on which it depends. ...
Definition: Phi.hpp:15
fvar< T > exp(const fvar< T > &x)
Definition: exp.hpp:11
vari * vi_
Pointer to the implementation of this variable.
Definition: var.hpp:45
fvar< T > Phi(const fvar< T > &x)
Definition: Phi.hpp:13
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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