#pragma once
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#include <functional>
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#include <vector>
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namespace torch {
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// NOTE: hash_combine is based on implementation from Boost
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//
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// Boost Software License - Version 1.0 - August 17th, 2003
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//
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// Permission is hereby granted, free of charge, to any person or organization
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// obtaining a copy of the software and accompanying documentation covered by
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// this license (the "Software") to use, reproduce, display, distribute,
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// execute, and transmit the Software, and to prepare derivative works of the
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// Software, and to permit third-parties to whom the Software is furnished to
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// do so, all subject to the following:
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//
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// The copyright notices in the Software and this entire statement, including
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// the above license grant, this restriction and the following disclaimer,
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// must be included in all copies of the Software, in whole or in part, and
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// all derivative works of the Software, unless such copies or derivative
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// works are solely in the form of machine-executable object code generated by
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// a source language processor.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
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// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
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// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
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// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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// DEALINGS IN THE SOFTWARE.
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inline size_t hash_combine(size_t seed, size_t value) {
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return seed ^ (value + 0x9e3779b9 + (seed << 6u) + (seed >> 2u));
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}
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////////////////////////////////////////////////////////////////////////////////
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// torch::hash implementation
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////////////////////////////////////////////////////////////////////////////////
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namespace _hash_detail {
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// Use template argument deduction to shorten calls to torch::hash
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template<typename T>
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size_t simple_get_hash(const T& o);
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template<typename T, typename V>
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using type_if_not_enum = typename std::enable_if<!std::is_enum<T>::value, V>::type;
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// Use SFINAE to dispatch to std::hash if possible, cast enum types to int automatically,
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// and fall back to T::hash otherwise.
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// NOTE: C++14 added support for hashing enum types to the standard, and some compilers
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// implement it even when C++14 flags aren't specified. This is why we have to disable
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// this overload if T is an enum type (and use the one below in this case).
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template<typename T>
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auto dispatch_hash(const T& o) -> decltype(std::hash<T>()(o), type_if_not_enum<T, size_t>()) {
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return std::hash<T>()(o);
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}
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template<typename T>
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typename std::enable_if<std::is_enum<T>::value, size_t>::type dispatch_hash(const T& o) {
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using R = typename std::underlying_type<T>::type;
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return std::hash<R>()(static_cast<R>(o));
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}
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template<typename T>
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auto dispatch_hash(const T& o) -> decltype(T::hash(o), size_t()) {
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return T::hash(o);
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}
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} // namespace _hash_detail
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// Hasher struct
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template<typename T>
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struct hash {
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size_t operator()(const T& o) const {
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return _hash_detail::dispatch_hash(o);
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};
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};
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// Specialization for std::tuple
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template<typename... Types>
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struct hash<std::tuple<Types...>> {
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template<size_t idx, typename... Ts>
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struct tuple_hash {
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size_t operator()(const std::tuple<Ts...>& t) const {
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return hash_combine(_hash_detail::simple_get_hash(std::get<idx>(t)),
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tuple_hash<idx-1, Ts...>()(t));
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}
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};
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template<typename... Ts>
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struct tuple_hash<0, Ts...> {
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size_t operator()(const std::tuple<Ts...>& t) const {
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return _hash_detail::simple_get_hash(std::get<0>(t));
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}
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};
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size_t operator()(const std::tuple<Types...>& t) const {
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return tuple_hash<sizeof...(Types)-1, Types...>()(t);
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}
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};
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// Specialization for std::vector
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template<typename T>
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struct hash<std::vector<T>> {
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size_t operator()(const std::vector<T>& v) const {
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size_t seed = 0;
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for (const auto & elem : v) {
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seed = hash_combine(seed, _hash_detail::simple_get_hash(elem));
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}
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return seed;
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}
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};
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namespace _hash_detail {
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template<typename T>
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size_t simple_get_hash(const T& o) {
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return torch::hash<T>()(o);
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}
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} // namespace _hash_detail
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// Use this function to actually hash multiple things in one line.
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// Dispatches to torch::hash, so it can hash containers.
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// Example:
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//
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// static size_t hash(const MyStruct& s) {
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// return get_hash(s.member1, s.member2, s.member3);
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// }
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template<typename... Types>
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size_t get_hash(const Types&... args) {
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return torch::hash<decltype(std::tie(args...))>()(std::tie(args...));
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}
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} // namespace torch
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