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inv_sqrt.hpp
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1#ifndef STAN_MATH_PRIM_FUN_INV_SQRT_HPP
2#define STAN_MATH_PRIM_FUN_INV_SQRT_HPP
3
10#include <cmath>
11
12namespace stan {
13namespace math {
14
15template <typename T, require_arithmetic_t<T>* = nullptr>
16inline auto inv_sqrt(const T x) {
17 return inv(std::sqrt(x));
18}
19
20template <typename T, require_complex_t<T>* = nullptr>
21inline auto inv_sqrt(const T x) {
22 return inv(sqrt(x));
23}
24
33 template <typename T>
34 static inline auto fun(T&& x) {
35 return inv_sqrt(std::forward<T>(x));
36 }
37};
38
47template <typename Container, require_ad_container_t<Container>* = nullptr>
48inline auto inv_sqrt(Container&& x) {
50 std::forward<Container>(x));
51}
52
61template <typename Container, require_not_var_matrix_t<Container>* = nullptr,
62 require_container_bt<std::is_arithmetic, Container>* = nullptr>
63inline auto inv_sqrt(Container&& x) {
64// Eigen 3.4.0 has precision issues on ARM64 with vectorised rsqrt
65// Resolved in current master branch, below can be removed on next release
66#ifdef __aarch64__
68 std::forward<Container>(x));
69#else
71 std::forward<Container>(x), [](auto&& v) { return v.array().rsqrt(); });
72#endif
73}
74
75} // namespace math
76} // namespace stan
77
78#endif
rsqrt_< as_operation_cl_t< T > > rsqrt(T &&a)
fvar< T > sqrt(const fvar< T > &x)
Definition sqrt.hpp:18
fvar< T > inv_sqrt(const fvar< T > &x)
Definition inv_sqrt.hpp:14
fvar< T > inv(const fvar< T > &x)
Definition inv.hpp:13
The lgamma implementation in stan-math is based on either the reentrant safe lgamma_r implementation ...
Base template class for vectorization of unary scalar functions defined by a template class F to a sc...
static auto fun(T &&x)
Definition inv_sqrt.hpp:34
Structure to wrap 1 / sqrt(x) so that it can be vectorized.
Definition inv_sqrt.hpp:32