inv_sqrt.hpp

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#ifndef STAN_MATH_OPENCL_REV_inv_sqrt_SQRT_HPP
#define STAN_MATH_OPENCL_REV_inv_sqrt_SQRT_HPP
#ifdef STAN_OPENCL
 
#include <stan/math/opencl/kernel_generator.hpp>
#include <stan/math/rev/core.hpp>
#include <stan/math/rev/fun/value_of.hpp>
 
namespace stan {
namespace math {
 
template <typename T,
          require_all_kernel_expressions_and_none_scalar_t<T>* = nullptr>
inline var_value<matrix_cl<double>> inv_sqrt(const var_value<T>& A) {
  return make_callback_var(
      inv_sqrt(A.val()), [A](vari_value<matrix_cl<double>>& res) mutable {
        A.adj()
            -= 0.5
               * elt_divide(res.adj(), elt_multiply(sqrt(A.val()), A.val()));
      });
}
 
}  // namespace math
}  // namespace stan
 
#endif
#endif