inv_logit.hpp

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#ifndef STAN_MATH_REV_FUN_INV_LOGIT_HPP
#define STAN_MATH_REV_FUN_INV_LOGIT_HPP
 
#include <stan/math/rev/meta.hpp>
#include <stan/math/rev/core.hpp>
#include <stan/math/prim/fun/inv_logit.hpp>
 
namespace stan {
namespace math {
 
template <typename T, require_stan_scalar_or_eigen_t<T>* = nullptr>
inline auto inv_logit(const var_value<T>& a) {
  return make_callback_var(inv_logit(a.val()), [a](auto& vi) mutable {
    as_array_or_scalar(a).adj() += as_array_or_scalar(vi.adj())
                                   * as_array_or_scalar(vi.val())
                                   * (1.0 - as_array_or_scalar(vi.val()));
  });
}
 
template <typename T, require_eigen_vt<is_var, T>* = nullptr>
inline auto inv_logit(T&& x) {
  auto x_arena = to_arena(std::forward<T>(x));
  arena_t<T> ret = inv_logit(x_arena.val());
  reverse_pass_callback([x_arena, ret]() mutable {
    x_arena.adj().array()
        += ret.adj().array() * ret.val().array() * (1.0 - ret.val().array());
  });
  return ret;
}
 
}  // namespace math
}  // namespace stan
#endif