Stan Math Library  2.15.0
reverse mode automatic differentiation
inv_square.hpp
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1 #ifndef STAN_MATH_REV_SCAL_FUN_INV_SQUARE_HPP
2 #define STAN_MATH_REV_SCAL_FUN_INV_SQUARE_HPP
3 
4 #include <stan/math/rev/core.hpp>
6 #include <valarray>
7 
8 namespace stan {
9  namespace math {
10 
11  namespace {
12  class inv_square_vari : public op_v_vari {
13  public:
14  explicit inv_square_vari(vari* avi) :
15  op_v_vari(inv_square(avi->val_), avi) {
16  }
17  void chain() {
18  avi_->adj_ -= 2 * adj_ / (avi_->val_ * avi_->val_ * avi_->val_);
19  }
20  };
21  }
22 
42  inline var inv_square(const var& a) {
43  return var(new inv_square_vari(a.vi_));
44  }
45 
46  }
47 }
48 #endif
Independent (input) and dependent (output) variables for gradients.
Definition: var.hpp:30
vari * vi_
Pointer to the implementation of this variable.
Definition: var.hpp:42
fvar< T > inv_square(const fvar< T > &x)
Definition: inv_square.hpp:14

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