Stan Math Library  2.14.0
reverse mode automatic differentiation
inv_sqrt.hpp
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1 #ifndef STAN_MATH_FWD_SCAL_FUN_INV_SQRT_HPP
2 #define STAN_MATH_FWD_SCAL_FUN_INV_SQRT_HPP
3 
4 #include <stan/math/fwd/core.hpp>
5 
6 #include <boost/math/tools/promotion.hpp>
7 
8 namespace stan {
9  namespace math {
10 
11  template <typename T>
12  inline
13  fvar<T>
14  inv_sqrt(const fvar<T>& x) {
15  using std::sqrt;
16  T sqrt_x(sqrt(x.val_));
17  return fvar<T>(1 / sqrt_x, -0.5 * x.d_ / (x.val_ * sqrt_x));
18  }
19  }
20 }
21 #endif
fvar< T > inv_sqrt(const fvar< T > &x)
Definition: inv_sqrt.hpp:14
fvar< T > sqrt(const fvar< T > &x)
Definition: sqrt.hpp:14

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