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inv_sqrt.hpp
Go to the documentation of this file.
1 #ifndef STAN_MATH_REV_SCAL_FUN_INV_SQRT_HPP
2 #define STAN_MATH_REV_SCAL_FUN_INV_SQRT_HPP
3
4 #include <stan/math/rev/core.hpp>
5 #include <stan/math/prim/scal/fun/inv_sqrt.hpp>
6 #include <valarray>
7
8 namespace stan {
9 namespace math {
10
11 namespace {
12 class inv_sqrt_vari : public op_v_vari {
13 public:
14 explicit inv_sqrt_vari(vari* avi) :
15 op_v_vari(stan::math::inv_sqrt(avi->val_), avi) {
16 }
17 void chain() {
18 avi_->adj_ -= 0.5 * adj_ / (avi_->val_ * std::sqrt(avi_->val_));
19 }
20 };
21 }
22
42 inline var inv_sqrt(const var& a) {
43 return var(new inv_sqrt_vari(a.vi_));
44 }
45
46 }
47 }
48 #endif
core.hpp
stan::math::inv_sqrt
fvar< T > inv_sqrt(const fvar< T > &x)
Definition: inv_sqrt.hpp:15
stan::math::sqrt
fvar< T > sqrt(const fvar< T > &x)
Definition: sqrt.hpp:15
stan::math::var
Independent (input) and dependent (output) variables for gradients.
Definition: var.hpp:32
stan::math::var::vi_
vari * vi_
Pointer to the implementation of this variable.
Definition: var.hpp:44
inv_sqrt.hpp

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