text: //          Copyright Malte Skarupke 2017.
  // Distributed under the Boost Software License, Version 1.0.
  //    (See http://www.boost.org/LICENSE_1_0.txt)
  
  #pragma once
  
  #include <cstdint>
  #include <cstddef>
  #include <functional>
  #include <cmath>
  #include <algorithm>
  #include <iterator>
  #include <stdexcept>
  #include <utility>
  #include <type_traits>
  
  #ifdef _MSC_VER
  #define SKA_NOINLINE(...) __declspec(noinline) __VA_ARGS__
  #else
  #define SKA_NOINLINE(...) __VA_ARGS__ __attribute__((noinline))
  #endif
  
  namespace ska
  {
  struct prime_number_hash_policy;
  struct power_of_two_hash_policy;
  struct fibonacci_hash_policy;
  
  namespace detailv3
  {
  template<typename Result, typename Functor>
  struct functor_storage : Functor
  {
      functor_storage() = default;
      functor_storage(const Functor & functor)
          : Functor(functor)
      {
      }
      template<typename... Args>
      Result operator()(Args &&... args)
      {
          return static_cast<Functor &>(*this)(std::forward<Args>(args)...);
      }
      template<typename... Args>
      Result operator()(Args &&... args) const
      {
          return static_cast<const Functor &>(*this)(std::forward<Args>(args)...);
      }
  };
  template<typename Result, typename... Args>
  struct functor_storage<Result, Result (*)(Args...)>
  {
      typedef Result (*function_ptr)(Args...);
      function_ptr function;
      functor_storage(function_ptr function)
          : function(function)
      {
      }
      Result operator()(Args... args) const
      {
          return function(std::forward<Args>(args)...);
      }
      operator function_ptr &()
      {
          return function;
      }
      operator const function_ptr &()
      {
          return function;
      }
  };
  template<typename key_type, typename value_type, typename hasher>
  struct KeyOrValueHasher : functor_storage<size_t, hasher>
  {
      typedef functor_storage<size_t, hasher> hasher_storage;
      KeyOrValueHasher() = default;
      KeyOrValueHasher(const hasher & hash)
          : hasher_storage(hash)
      {
      }
      size_t operator()(const key_type & key)
      {
          return static_cast<hasher_storage &>(*this)(key);
      }
      size_t operator()(const key_type & key) const
      {
          return static_cast<const hasher_storage &>(*this)(key);
      }
      size_t operator()(const value_type & value)
      {
          return static_cast<hasher_storage &>(*this)(value.first);
      }
      size_t operator()(const value_type & value) const
      {
          return static_cast<const hasher_storage &>(*this)(value.first);
      }
      template<typename F, typename S>
      size_t operator()(const std::pair<F, S> & value)
      {
          return static_cast<hasher_storage &>(*this)(value.first);
      }
      template<typename F, typename S>
      size_t operator()(const std::pair<F, S> & value) const
      {
          return static_cast<const hasher_storage &>(*this)(value.first);
      }
  };
  template<typename key_type, typename value_type, typename key_equal>
  struct KeyOrValueEquality : functor_storage<bool, key_equal>
  {
      typedef functor_storage<bool, key_equal> equality_storage;
      KeyOrValueEquality() = default;
      KeyOrValueEquality(const key_equal & equality)
          : equality_storage(equality)
      {
      }
      bool operator()(const key_type & lhs, const key_type & rhs)
      {
          return static_cast<equality_storage &>(*this)(lhs, rhs);
      }
      bool operator()(const key_type & lhs, const value_type & rhs)
      {
          return static_cast<equality_storage &>(*this)(lhs, rhs.first);
      }
      bool operator()(const value_type & lhs, const key_type & rhs)
      {
          return static_cast<equality_storage &>(*this)(lhs.first, rhs);
      }
      bool operator()(const value_type & lhs, const value_type & rhs)
      {
          return static_cast<equality_storage &>(*this)(lhs.first, rhs.first);
      }
      template<typename F, typename S>
      bool operator()(const key_type & lhs, const std::pair<F, S> & rhs)
      {
          return static_cast<equality_storage &>(*this)(lhs, rhs.first);
      }
      template<typename F, typename S>
      bool operator()(const std::pair<F, S> & lhs, const key_type & rhs)
      {
          return static_cast<equality_storage &>(*this)(lhs.first, rhs);
      }
      template<typename F, typename S>
      bool operator()(const value_type & lhs, const std::pair<F, S> & rhs)
      {
          return static_cast<equality_storage &>(*this)(lhs.first, rhs.first);
      }
      template<typename F, typename S>
      bool operator()(const std::pair<F, S> & lhs, const value_type & rhs)
      {
          return static_cast<equality_storage &>(*this)(lhs.first, rhs.first);
      }
      template<typename FL, typename SL, typename FR, typename SR>
      bool operator()(const std::pair<FL, SL> & lhs, const std::pair<FR, SR> & rhs)
      {
          return static_cast<equality_storage &>(*this)(lhs.first, rhs.first);
      }
  };
  static constexpr int8_t min_lookups = 4;
  template<typename T>
  struct sherwood_v3_entry
  {
      sherwood_v3_entry()
      {
      }
      sherwood_v3_entry(int8_t distance_from_desired)
          : distance_from_desired(distance_from_desired)
      {
      }
      ~sherwood_v3_entry()
      {
      }
      static sherwood_v3_entry * empty_default_table()
      {
          static sherwood_v3_entry result[min_lookups] = { {}, {}, {}, {special_end_value} };
          return result;
      }
  
      bool has_value() const
      {
          return distance_from_desired >= 0;
      }
      bool is_empty() const
      {
          return distance_from_desired < 0;
      }
      bool is_at_desired_position() const
      {
          return distance_from_desired <= 0;
      }
      template<typename... Args>
      void emplace(int8_t distance, Args &&... args)
      {
          new (std::addressof(value)) T(std::forward<Args>(args)...);
          distance_from_desired = distance;
      }
  
      void destroy_value()
      {
          value.~T();
          distance_from_desired = -1;
      }
  
      int8_t distance_from_desired = -1;
      static constexpr int8_t special_end_value = 0;
      union { T value; };
  };
  
  inline int8_t log2(size_t value)
  {
      static constexpr int8_t table[64] =
      {
          63,  0, 58,  1, 59, 47, 53,  2,
          60, 39, 48, 27, 54, 33, 42,  3,
          61, 51, 37, 40, 49, 18, 28, 20,
          55, 30, 34, 11, 43, 14, 22,  4,
          62, 57, 46, 52, 38, 26, 32, 41,
          50, 36, 17, 19, 29, 10, 13, 21,
          56, 45, 25, 31, 35, 16,  9, 12,
          44, 24, 15,  8, 23,  7,  6,  5
      };
      value |= value >> 1;
      value |= value >> 2;
      value |= value >> 4;
      value |= value >> 8;
      value |= value >> 16;
      value |= value >> 32;
      return table[((value - (value >> 1)) * 0x07EDD5E59A4E28C2) >> 58];
  }
  
  template<typename T, bool>
  struct AssignIfTrue
  {
      void operator()(T & lhs, const T & rhs)
      {
          lhs = rhs;
      }
      void operator()(T & lhs, T && rhs)
      {
          lhs = std::move(rhs);
      }
  };
  template<typename T>
  struct AssignIfTrue<T, false>
  {
      void operator()(T &, const T &)
      {
      }
      void operator()(T &, T &&)
      {
      }
  };
  
  inline size_t next_power_of_two(size_t i)
  {
      --i;
      i |= i >> 1;
      i |= i >> 2;
      i |= i >> 4;
      i |= i >> 8;
      i |= i >> 16;
      i |= i >> 32;
      ++i;
      return i;
  }
  
  template<typename...> using void_t = void;
  
  template<typename T, typename = void>
  struct HashPolicySelector
  {
      typedef fibonacci_hash_policy type;
  };
  template<typename T>
  struct HashPolicySelector<T, void_t<typename T::hash_policy>>
  {
      typedef typename T::hash_policy type;
  };
  
  template<typename T, typename FindKey, typename ArgumentHash, typename Hasher, typename ArgumentEqual, typename Equal, typename ArgumentAlloc, typename EntryAlloc>
  class sherwood_v3_table : private EntryAlloc, private Hasher, private Equal
  {
      using Entry = detailv3::sherwood_v3_entry<T>;
      using AllocatorTraits = std::allocator_traits<EntryAlloc>;
      using EntryPointer = typename AllocatorTraits::pointer;
      struct convertible_to_iterator;
  
  public:
  
      using value_type = T;
      using size_type = size_t;
      using difference_type = std::ptrdiff_t;
      using hasher = ArgumentHash;
      using key_equal = ArgumentEqual;
      using allocator_type = EntryAlloc;
      using reference = value_type &;
      using const_reference = const value_type &;
      using pointer = value_type *;
      using const_pointer = const value_type *;
  
      sherwood_v3_table()
      {
      }
      explicit sherwood_v3_table(size_type bucket_count, const ArgumentHash & hash = ArgumentHash(), const ArgumentEqual & equal = ArgumentEqual(), const ArgumentAlloc & alloc = ArgumentAlloc())
          : EntryAlloc(alloc), Hasher(hash), Equal(equal)
      {
          rehash(bucket_count);
      }
      sherwood_v3_table(size_type bucket_count, const ArgumentAlloc & alloc)
          : sherwood_v3_table(bucket_count, ArgumentHash(), ArgumentEqual(), alloc)
      {
      }
      sherwood_v3_table(size_type bucket_count, const ArgumentHash & hash, const ArgumentAlloc & alloc)
          : sherwood_v3_table(bucket_count, hash, ArgumentEqual(), alloc)
      {
      }
      explicit sherwood_v3_table(const ArgumentAlloc & alloc)
          : EntryAlloc(alloc)
      {
      }
      template<typename It>
      sherwood_v3_table(It first, It last, size_type bucket_count = 0, const ArgumentHash & hash = ArgumentHash(), const ArgumentEqual & equal = ArgumentEqual(), const ArgumentAlloc & alloc = ArgumentAlloc())
          : sherwood_v3_table(bucket_count, hash, equal, alloc)
      {
          insert(first, last);
      }
      template<typename It>
      sherwood_v3_table(It first, It last, size_type bucket_count, const ArgumentAlloc & alloc)
          : sherwood_v3_table(first, last, bucket_count, ArgumentHash(), ArgumentEqual(), alloc)
      {
      }
      template<typename It>
      sherwood_v3_table(It first, It last, size_type bucket_count, const ArgumentHash & hash, const ArgumentAlloc & alloc)
          : sherwood_v3_table(first, last, bucket_count, hash, ArgumentEqual(), alloc)
      {
      }
      sherwood_v3_table(std::initializer_list<T> il, size_type bucket_count = 0, const ArgumentHash & hash = ArgumentHash(), const ArgumentEqual & equal = ArgumentEqual(), const ArgumentAlloc & alloc = ArgumentAlloc())
          : sherwood_v3_table(bucket_count, hash, equal, alloc)
      {
          if (bucket_count == 0)
              rehash(il.size());
          insert(il.begin(), il.end());
      }
      sherwood_v3_table(std::initializer_list<T> il, size_type bucket_count, const ArgumentAlloc & alloc)
          : sherwood_v3_table(il, bucket_count, ArgumentHash(), ArgumentEqual(), alloc)
      {
      }
      sherwood_v3_table(std::initializer_list<T> il, size_type bucket_count, const ArgumentHash & hash, const ArgumentAlloc & alloc)
          : sherwood_v3_table(il, bucket_count, hash, ArgumentEqual(), alloc)
      {
      }
      sherwood_v3_table(const sherwood_v3_table & other)
          : sherwood_v3_table(other, AllocatorTraits::select_on_container_copy_construction(other.get_allocator()))
      {
      }
      sherwood_v3_table(const sherwood_v3_table & other, const ArgumentAlloc & alloc)
          : EntryAlloc(alloc), Hasher(other), Equal(other), _max_load_factor(other._max_load_factor)
      {
          rehash_for_other_container(other);
          try
          {
              insert(other.begin(), other.end());
          }
          catch(...)
          {
              clear();
              deallocate_data(entries, num_slots_minus_one, max_lookups);
              throw;
          }
      }
      sherwood_v3_table(sherwood_v3_table && other) noexcept
          : EntryAlloc(std::move(other)), Hasher(std::move(other)), Equal(std::move(other))
      {
          swap_pointers(other);
      }
      sherwood_v3_table(sherwood_v3_table && other, const ArgumentAlloc & alloc) noexcept
          : EntryAlloc(alloc), Hasher(std::move(other)), Equal(std::move(other))
      {
          swap_pointers(other);
      }
      sherwood_v3_table & operator=(const sherwood_v3_table & other)
      {
          if (this == std::addressof(other))
              return *this;
  
          clear();
          if (AllocatorTraits::propagate_on_container_copy_assignment::value)
          {
              if (static_cast<EntryAlloc &>(*this) != static_cast<const EntryAlloc &>(other))
              {
                  reset_to_empty_state();
              }
              AssignIfTrue<EntryAlloc, AllocatorTraits::propagate_on_container_copy_assignment::value>()(*this, other);
          }
          _max_load_factor = other._max_load_factor;
          static_cast<Hasher &>(*this) = other;
          static_cast<Equal &>(*this) = other;
          rehash_for_other_container(other);
          insert(other.begin(), other.end());
          return *this;
      }
      sherwood_v3_table & operator=(sherwood_v3_table && other) noexcept
      {
          if (this == std::addressof(other))
              return *this;
          else if (AllocatorTraits::propagate_on_container_move_assignment::value)
          {
              clear();
              reset_to_empty_state();
              AssignIfTrue<EntryAlloc, AllocatorTraits::propagate_on_container_move_assignment::value>()(*this, std::move(other));
              swap_pointers(other);
          }
          else if (static_cast<EntryAlloc &>(*this) == static_cast<EntryAlloc &>(other))
          {
              swap_pointers(other);
          }
          else
          {
              clear();
              _max_load_factor = other._max_load_factor;
              rehash_for_other_container(other);
              for (T & elem : other)
                  emplace(std::move(elem));
              other.clear();
          }
          static_cast<Hasher &>(*this) = std::move(other);
          static_cast<Equal &>(*this) = std::move(other);
          return *this;
      }
      ~sherwood_v3_table()
      {
          clear();
          deallocate_data(entries, num_slots_minus_one, max_lookups);
      }
  
      const allocator_type & get_allocator() const
      {
          return static_cast<const allocator_type &>(*this);
      }
      const ArgumentEqual & key_eq() const
      {
          return static_cast<const ArgumentEqual &>(*this);
      }
      const ArgumentHash & hash_function() const
      {
          return static_cast<const ArgumentHash &>(*this);
      }
  
      template<typename ValueType>
      struct templated_iterator
      {
          templated_iterator() = default;
          templated_iterator(EntryPointer current)
              : current(current)
          {
          }
          EntryPointer current = EntryPointer();
  
          using iterator_category = std::forward_iterator_tag;
          using value_type = ValueType;
          using difference_type = ptrdiff_t;
          using pointer = ValueType *;
          using reference = ValueType &;
  
          friend bool operator==(const templated_iterator & lhs, const templated_iterator & rhs)
          {
              return lhs.current == rhs.current;
          }
          friend bool operator!=(const templated_iterator & lhs, const templated_iterator & rhs)
          {
              return !(lhs == rhs);
          }
  
          templated_iterator & operator++()
          {
              do
              {
                  ++current;
              }
              while(current->is_empty());
              return *this;
          }
          templated_iterator operator++(int)
          {
              templated_iterator copy(*this);
              ++*this;
              return copy;
          }
  
          ValueType & operator*() const
          {
              return current->value;
          }
          ValueType * operator->() const
          {
              return std::addressof(current->value);
          }
  
          operator templated_iterator<const value_type>() const
          {
              return { current };
          }
      };
      using iterator = templated_iterator<value_type>;
      using const_iterator = templated_iterator<const value_type>;
  
      iterator begin()
      {
          for (EntryPointer it = entries;; ++it)
          {
              if (it->has_value())
                  return { it };
          }
      }
      const_iterator begin() const
      {
          for (EntryPointer it = entries;; ++it)
          {
              if (it->has_value())
                  return { it };
          }
      }
      const_iterator cbegin() const
      {
          return begin();
      }
      iterator end()
      {
          return { entries + static_cast<ptrdiff_t>(num_slots_minus_one + max_lookups) };
      }
      const_iterator end() const
      {
          return { entries + static_cast<ptrdiff_t>(num_slots_minus_one + max_lookups) };
      }
      const_iterator cend() const
      {
          return end();
      }
  
      iterator find(const FindKey & key)
      {
          size_t index = hash_policy.index_for_hash(hash_object(key), num_slots_minus_one);
          EntryPointer it = entries + ptrdiff_t(index);
          for (int8_t distance = 0; it->distance_from_desired >= distance; ++distance, ++it)
          {
              if (compares_equal(key, it->value))
                  return { it };
          }
          return end();
      }
      const_iterator find(const FindKey & key) const
      {
          return const_cast<sherwood_v3_table *>(this)->find(key);
      }
      size_t count(const FindKey & key) const
      {
          return find(key) == end() ? 0 : 1;
      }
      std::pair<iterator, iterator> equal_range(const FindKey & key)
      {
          iterator found = find(key);
          if (found == end())
              return { found, found };
          else
              return { found, std::next(found) };
      }
      std::pair<const_iterator, const_iterator> equal_range(const FindKey & key) const
      {
          const_iterator found = find(key);
          if (found == end())
              return { found, found };
          else
              return { found, std::next(found) };
      }
  
      template<typename Key, typename... Args>
      std::pair<iterator, bool> emplace(Key && key, Args &&... args)
      {
          size_t index = hash_policy.index_for_hash(hash_object(key), num_slots_minus_one);
          EntryPointer current_entry = entries + ptrdiff_t(index);
          int8_t distance_from_desired = 0;
          for (; current_entry->distance_from_desired >= distance_from_desired; ++current_entry, ++distance_from_desired)
          {
              if (compares_equal(key, current_entry->value))
                  return { { current_entry }, false };
          }
          return emplace_new_key(distance_from_desired, current_entry, std::forward<Key>(key), std::forward<Args>(args)...);
      }
  
      std::pair<iterator, bool> insert(const value_type & value)
      {
          return emplace(value);
      }
      std::pair<iterator, bool> insert(value_type && value)
      {
          return emplace(std::move(value));
      }
      template<typename... Args>
      iterator emplace_hint(const_iterator, Args &&... args)
      {
          return emplace(std::forward<Args>(args)...).first;
      }
      iterator insert(const_iterator, const value_type & value)
      {
          return emplace(value).first;
      }
      iterator insert(const_iterator, value_type && value)
      {
          return emplace(std::move(value)).first;
      }
  
      template<typename It>
      void insert(It begin, It end)
      {
          for (; begin != end; ++begin)
          {
              emplace(*begin);
          }
      }
      void insert(std::initializer_list<value_type> il)
      {
          insert(il.begin(), il.end());
      }
  
      void rehash(size_t num_buckets)
      {
          num_buckets = std::max(num_buckets, static_cast<size_t>(std::ceil(num_elements / static_cast<double>(_max_load_factor))));
          if (num_buckets == 0)
          {
              reset_to_empty_state();
              return;
          }
          auto new_prime_index = hash_policy.next_size_over(num_buckets);
          if (num_buckets == bucket_count())
              return;
          int8_t new_max_lookups = compute_max_lookups(num_buckets);
          EntryPointer new_buckets(AllocatorTraits::allocate(*this, num_buckets + new_max_lookups));
          EntryPointer special_end_item = new_buckets + static_cast<ptrdiff_t>(num_buckets + new_max_lookups - 1);
          for (EntryPointer it = new_buckets; it != special_end_item; ++it)
              it->distance_from_desired = -1;
          special_end_item->distance_from_desired = Entry::special_end_value;
          std::swap(entries, new_buckets);
          std::swap(num_slots_minus_one, num_buckets);
          --num_slots_minus_one;
          hash_policy.commit(new_prime_index);
          int8_t old_max_lookups = max_lookups;
          max_lookups = new_max_lookups;
          num_elements = 0;
          for (EntryPointer it = new_buckets, end = it + static_cast<ptrdiff_t>(num_buckets + old_max_lookups); it != end; ++it)
          {
              if (it->has_value())
              {
                  emplace(std::move(it->value));
                  it->destroy_value();
              }
          }
          deallocate_data(new_buckets, num_buckets, old_max_lookups);
      }
  
      void reserve(size_t num_elements)
      {
          size_t required_buckets = num_buckets_for_reserve(num_elements);
          if (required_buckets > bucket_count())
              rehash(required_buckets);
      }
  
      // the return value is a type that can be converted to an iterator
      // the reason for doing this is that it's not free to find the
      // iterator pointing at the next element. if you care about the
      // next iterator, turn the return value into an iterator
      convertible_to_iterator erase(const_iterator to_erase)
      {
          EntryPointer current = to_erase.current;
          current->destroy_value();
          --num_elements;
          for (EntryPointer next = current + ptrdiff_t(1); !next->is_at_desired_position(); ++current, ++next)
          {
              current->emplace(next->distance_from_desired - 1, std::move(next->value));
              next->destroy_value();
          }
          return { to_erase.current };
      }
  
      iterator erase(const_iterator begin_it, const_iterator end_it)
      {
          if (begin_it == end_it)
              return { begin_it.current };
          for (EntryPointer it = begin_it.current, end = end_it.current; it != end; ++it)
          {
              if (it->has_value())
              {
                  it->destroy_value();
                  --num_elements;
              }
          }
          if (end_it == this->end())
              return this->end();
          ptrdiff_t num_to_move = std::min(static_cast<ptrdiff_t>(end_it.current->distance_from_desired), end_it.current - begin_it.current);
          EntryPointer to_return = end_it.current - num_to_move;
          for (EntryPointer it = end_it.current; !it->is_at_desired_position();)
          {
              EntryPointer target = it - num_to_move;
              target->emplace(it->distance_from_desired - num_to_move, std::move(it->value));
              it->destroy_value();
              ++it;
              num_to_move = std::min(static_cast<ptrdiff_t>(it->distance_from_desired), num_to_move);
          }
          return { to_return };
      }
  
      size_t erase(const FindKey & key)
      {
          auto found = find(key);
          if (found == end())
              return 0;
          else
          {
              erase(found);
              return 1;
          }
      }
  
      void clear()
      {
          for (EntryPointer it = entries, end = it + static_cast<ptrdiff_t>(num_slots_minus_one + max_lookups); it != end; ++it)
          {
              if (it->has_value())
                  it->destroy_value();
          }
          num_elements = 0;
      }
  
      void shrink_to_fit()
      {
          rehash_for_other_container(*this);
      }
  
      void swap(sherwood_v3_table & other)
      {
          using std::swap;
          swap_pointers(other);
          swap(static_cast<ArgumentHash &>(*this), static_cast<ArgumentHash &>(other));
          swap(static_cast<ArgumentEqual &>(*this), static_cast<ArgumentEqual &>(other));
          if (AllocatorTraits::propagate_on_container_swap::value)
              swap(static_cast<EntryAlloc &>(*this), static_cast<EntryAlloc &>(other));
      }
  
      size_t size() const
      {
          return num_elements;
      }
      size_t max_size() const
      {
          return (AllocatorTraits::max_size(*this)) / sizeof(Entry);
      }
      size_t bucket_count() const
      {
          return num_slots_minus_one ? num_slots_minus_one + 1 : 0;
      }
      size_type max_bucket_count() const
      {
          return (AllocatorTraits::max_size(*this) - min_lookups) / sizeof(Entry);
      }
      size_t bucket(const FindKey & key) const
      {
          return hash_policy.index_for_hash(hash_object(key), num_slots_minus_one);
      }
      float load_factor() const
      {
          size_t buckets = bucket_count();
          if (buckets)
              return static_cast<float>(num_elements) / bucket_count();
          else
              return 0;
      }
      void max_load_factor(float value)
      {
          _max_load_factor = value;
      }
      float max_load_factor() const
      {
          return _max_load_factor;
      }
  
      bool empty() const
      {
          return num_elements == 0;
      }
  
  private:
      EntryPointer entries = Entry::empty_default_table();
      size_t num_slots_minus_one = 0;
      typename HashPolicySelector<ArgumentHash>::type hash_policy;
      int8_t max_lookups = detailv3::min_lookups - 1;
      float _max_load_factor = 0.5f;
      size_t num_elements = 0;
  
      static int8_t compute_max_lookups(size_t num_buckets)
      {
          int8_t desired = detailv3::log2(num_buckets);
          return std::max(detailv3::min_lookups, desired);
      }
  
      size_t num_buckets_for_reserve(size_t num_elements) const
      {
          return static_cast<size_t>(std::ceil(num_elements / std::min(0.5, static_cast<double>(_max_load_factor))));
      }
      void rehash_for_other_container(const sherwood_v3_table & other)
      {
          rehash(std::min(num_buckets_for_reserve(other.size()), other.bucket_count()));
      }
  
      void swap_pointers(sherwood_v3_table & other)
      {
          using std::swap;
          swap(hash_policy, other.hash_policy);
          swap(entries, other.entries);
          swap(num_slots_minus_one, other.num_slots_minus_one);
          swap(num_elements, other.num_elements);
          swap(max_lookups, other.max_lookups);
          swap(_max_load_factor, other._max_load_factor);
      }
  
      template<typename Key, typename... Args>
      SKA_NOINLINE(std::pair<iterator, bool>) emplace_new_key(int8_t distance_from_desired, EntryPointer current_entry, Key && key, Args &&... args)
      {
          using std::swap;
          if (num_slots_minus_one == 0 || distance_from_desired == max_lookups || num_elements + 1 > (num_slots_minus_one + 1) * static_cast<double>(_max_load_factor))
          {
              grow();
              return emplace(std::forward<Key>(key), std::forward<Args>(args)...);
          }
          else if (current_entry->is_empty())
          {
              current_entry->emplace(distance_from_desired, std::forward<Key>(key), std::forward<Args>(args)...);
              ++num_elements;
              return { { current_entry }, true };
          }
          value_type to_insert(std::forward<Key>(key), std::forward<Args>(args)...);
          swap(distance_from_desired, current_entry->distance_from_desired);
          swap(to_insert, current_entry->value);
          iterator result = { current_entry };
          for (++distance_from_desired, ++current_entry;; ++current_entry)
          {
              if (current_entry->is_empty())
              {
                  current_entry->emplace(distance_from_desired, std::move(to_insert));
                  ++num_elements;
                  return { result, true };
              }
              else if (current_entry->distance_from_desired < distance_from_desired)
              {
                  swap(distance_from_desired, current_entry->distance_from_desired);
                  swap(to_insert, current_entry->value);
                  ++distance_from_desired;
              }
              else
              {
                  ++distance_from_desired;
                  if (distance_from_desired == max_lookups)
                  {
                      swap(to_insert, result.current->value);
                      grow();
                      return emplace(std::move(to_insert));
                  }
              }
          }
      }
  
      void grow()
      {
          rehash(std::max(size_t(4), 2 * bucket_count()));
      }
  
      void deallocate_data(EntryPointer begin, size_t num_slots_minus_one, int8_t max_lookups)
      {
          if (begin != Entry::empty_default_table())
          {
              AllocatorTraits::deallocate(*this, begin, num_slots_minus_one + max_lookups + 1);
          }
      }
  
      void reset_to_empty_state()
      {
          deallocate_data(entries, num_slots_minus_one, max_lookups);
          entries = Entry::empty_default_table();
          num_slots_minus_one = 0;
          hash_policy.reset();
          max_lookups = detailv3::min_lookups - 1;
      }
  
      template<typename U>
      size_t hash_object(const U & key)
      {
          return static_cast<Hasher &>(*this)(key);
      }
      template<typename U>
      size_t hash_object(const U & key) const
      {
          return static_cast<const Hasher &>(*this)(key);
      }
      template<typename L, typename R>
      bool compares_equal(const L & lhs, const R & rhs)
      {
          return static_cast<Equal &>(*this)(lhs, rhs);
      }
  
      struct convertible_to_iterator
      {
          EntryPointer it;
  
          operator iterator()
          {
              if (it->has_value())
                  return { it };
              else
                  return ++iterator{it};
          }
          operator const_iterator()
          {
              if (it->has_value())
                  return { it };
              else
                  return ++const_iterator{it};
          }
      };
  
  };
  }
  
  struct prime_number_hash_policy
  {
      static size_t mod0(size_t) { return 0llu; }
      static size_t mod2(size_t hash) { return hash % 2llu; }
      static size_t mod3(size_t hash) { return hash % 3llu; }
      static size_t mod5(size_t hash) { return hash % 5llu; }
      static size_t mod7(size_t hash) { return hash % 7llu; }
      static size_t mod11(size_t hash) { return hash % 11llu; }
      static size_t mod13(size_t hash) { return hash % 13llu; }
      static size_t mod17(size_t hash) { return hash % 17llu; }
      static size_t mod23(size_t hash) { return hash % 23llu; }
      static size_t mod29(size_t hash) { return hash % 29llu; }
      static size_t mod37(size_t hash) { return hash % 37llu; }
      static size_t mod47(size_t hash) { return hash % 47llu; }
      static size_t mod59(size_t hash) { return hash % 59llu; }
      static size_t mod73(size_t hash) { return hash % 73llu; }
      static size_t mod97(size_t hash) { return hash % 97llu; }
      static size_t mod127(size_t hash) { return hash % 127llu; }
      static size_t mod151(size_t hash) { return hash % 151llu; }
      static size_t mod197(size_t hash) { return hash % 197llu; }
      static size_t mod251(size_t hash) { return hash % 251llu; }
      static size_t mod313(size_t hash) { return hash % 313llu; }
      static size_t mod397(size_t hash) { return hash % 397llu; }
      static size_t mod499(size_t hash) { return hash % 499llu; }
      static size_t mod631(size_t hash) { return hash % 631llu; }
      static size_t mod797(size_t hash) { return hash % 797llu; }
      static size_t mod1009(size_t hash) { return hash % 1009llu; }
      static size_t mod1259(size_t hash) { return hash % 1259llu; }
      static size_t mod1597(size_t hash) { return hash % 1597llu; }
      static size_t mod2011(size_t hash) { return hash % 2011llu; }
      static size_t mod2539(size_t hash) { return hash % 2539llu; }
      static size_t mod3203(size_t hash) { return hash % 3203llu; }
      static size_t mod4027(size_t hash) { return hash % 4027llu; }
      static size_t mod5087(size_t hash) { return hash % 5087llu; }
      static size_t mod6421(size_t hash) { return hash % 6421llu; }
      static size_t mod8089(size_t hash) { return hash % 8089llu; }
      static size_t mod10193(size_t hash) { return hash % 10193llu; }
      static size_t mod12853(size_t hash) { return hash % 12853llu; }
      static size_t mod16193(size_t hash) { return hash % 16193llu; }
      static size_t mod20399(size_t hash) { return hash % 20399llu; }
      static size_t mod25717(size_t hash) { return hash % 25717llu; }
      static size_t mod32401(size_t hash) { return hash % 32401llu; }
      static size_t mod40823(size_t hash) { return hash % 40823llu; }
      static size_t mod51437(size_t hash) { return hash % 51437llu; }
      static size_t mod64811(size_t hash) { return hash % 64811llu; }
      static size_t mod81649(size_t hash) { return hash % 81649llu; }
      static size_t mod102877(size_t hash) { return hash % 102877llu; }
      static size_t mod129607(size_t hash) { return hash % 129607llu; }
      static size_t mod163307(size_t hash) { return hash % 163307llu; }
      static size_t mod205759(size_t hash) { return hash % 205759llu; }
      static size_t mod259229(size_t hash) { return hash % 259229llu; }
      static size_t mod326617(size_t hash) { return hash % 326617llu; }
      static size_t mod411527(size_t hash) { return hash % 411527llu; }
      static size_t mod518509(size_t hash) { return hash % 518509llu; }
      static size_t mod653267(size_t hash) { return hash % 653267llu; }
      static size_t mod823117(size_t hash) { return hash % 823117llu; }
      static size_t mod1037059(size_t hash) { return hash % 1037059llu; }
      static size_t mod1306601(size_t hash) { return hash % 1306601llu; }
      static size_t mod1646237(size_t hash) { return hash % 1646237llu; }
      static size_t mod2074129(size_t hash) { return hash % 2074129llu; }
      static size_t mod2613229(size_t hash) { return hash % 2613229llu; }
      static size_t mod3292489(size_t hash) { return hash % 3292489llu; }
      static size_t mod4148279(size_t hash) { return hash % 4148279llu; }
      static size_t mod5226491(size_t hash) { return hash % 5226491llu; }
      static size_t mod6584983(size_t hash) { return hash % 6584983llu; }
      static size_t mod8296553(size_t hash) { return hash % 8296553llu; }
      static size_t mod10453007(size_t hash) { return hash % 10453007llu; }
      static size_t mod13169977(size_t hash) { return hash % 13169977llu; }
      static size_t mod16593127(size_t hash) { return hash % 16593127llu; }
      static size_t mod20906033(size_t hash) { return hash % 20906033llu; }
      static size_t mod26339969(size_t hash) { return hash % 26339969llu; }
      static size_t mod33186281(size_t hash) { return hash % 33186281llu; }
      static size_t mod41812097(size_t hash) { return hash % 41812097llu; }
      static size_t mod52679969(size_t hash) { return hash % 52679969llu; }
      static size_t mod66372617(size_t hash) { return hash % 66372617llu; }
      static size_t mod83624237(size_t hash) { return hash % 83624237llu; }
      static size_t mod105359939(size_t hash) { return hash % 105359939llu; }
      static size_t mod132745199(size_t hash) { return hash % 132745199llu; }
      static size_t mod167248483(size_t hash) { return hash % 167248483llu; }
      static size_t mod210719881(size_t hash) { return hash % 210719881llu; }
      static size_t mod265490441(size_t hash) { return hash % 265490441llu; }
      static size_t mod334496971(size_t hash) { return hash % 334496971llu; }
      static size_t mod421439783(size_t hash) { return hash % 421439783llu; }
      static size_t mod530980861(size_t hash) { return hash % 530980861llu; }
      static size_t mod668993977(size_t hash) { return hash % 668993977llu; }
      static size_t mod842879579(size_t hash) { return hash % 842879579llu; }
      static size_t mod1061961721(size_t hash) { return hash % 1061961721llu; }
      static size_t mod1337987929(size_t hash) { return hash % 1337987929llu; }
      static size_t mod1685759167(size_t hash) { return hash % 1685759167llu; }
      static size_t mod2123923447(size_t hash) { return hash % 2123923447llu; }
      static size_t mod2675975881(size_t hash) { return hash % 2675975881llu; }
      static size_t mod3371518343(size_t hash) { return hash % 3371518343llu; }
      static size_t mod4247846927(size_t hash) { return hash % 4247846927llu; }
      static size_t mod5351951779(size_t hash) { return hash % 5351951779llu; }
      static size_t mod6743036717(size_t hash) { return hash % 6743036717llu; }
      static size_t mod8495693897(size_t hash) { return hash % 8495693897llu; }
      static size_t mod10703903591(size_t hash) { return hash % 10703903591llu; }
      static size_t mod13486073473(size_t hash) { return hash % 13486073473llu; }
      static size_t mod16991387857(size_t hash) { return hash % 16991387857llu; }
      static size_t mod21407807219(size_t hash) { return hash % 21407807219llu; }
      static size_t mod26972146961(size_t hash) { return hash % 26972146961llu; }
      static size_t mod33982775741(size_t hash) { return hash % 33982775741llu; }
      static size_t mod42815614441(size_t hash) { return hash % 42815614441llu; }
      static size_t mod53944293929(size_t hash) { return hash % 53944293929llu; }
      static size_t mod67965551447(size_t hash) { return hash % 67965551447llu; }
      static size_t mod85631228929(size_t hash) { return hash % 85631228929llu; }
      static size_t mod107888587883(size_t hash) { return hash % 107888587883llu; }
      static size_t mod135931102921(size_t hash) { return hash % 135931102921llu; }
      static size_t mod171262457903(size_t hash) { return hash % 171262457903llu; }
      static size_t mod215777175787(size_t hash) { return hash % 215777175787llu; }
      static size_t mod271862205833(size_t hash) { return hash % 271862205833llu; }
      static size_t mod342524915839(size_t hash) { return hash % 342524915839llu; }
      static size_t mod431554351609(size_t hash) { return hash % 431554351609llu; }
      static size_t mod543724411781(size_t hash) { return hash % 543724411781llu; }
      static size_t mod685049831731(size_t hash) { return hash % 685049831731llu; }
      static size_t mod863108703229(size_t hash) { return hash % 863108703229llu; }
      static size_t mod1087448823553(size_t hash) { return hash % 1087448823553llu; }
      static size_t mod1370099663459(size_t hash) { return hash % 1370099663459llu; }
      static size_t mod1726217406467(size_t hash) { return hash % 1726217406467llu; }
      static size_t mod2174897647073(size_t hash) { return hash % 2174897647073llu; }
      static size_t mod2740199326961(size_t hash) { return hash % 2740199326961llu; }
      static size_t mod3452434812973(size_t hash) { return hash % 3452434812973llu; }
      static size_t mod4349795294267(size_t hash) { return hash % 4349795294267llu; }
      static size_t mod5480398654009(size_t hash) { return hash % 5480398654009llu; }
      static size_t mod6904869625999(size_t hash) { return hash % 6904869625999llu; }
      static size_t mod8699590588571(size_t hash) { return hash % 8699590588571llu; }
      static size_t mod10960797308051(size_t hash) { return hash % 10960797308051llu; }
      static size_t mod13809739252051(size_t hash) { return hash % 13809739252051llu; }
      static size_t mod17399181177241(size_t hash) { return hash % 17399181177241llu; }
      static size_t mod21921594616111(size_t hash) { return hash % 21921594616111llu; }
      static size_t mod27619478504183(size_t hash) { return hash % 27619478504183llu; }
      static size_t mod34798362354533(size_t hash) { return hash % 34798362354533llu; }
      static size_t mod43843189232363(size_t hash) { return hash % 43843189232363llu; }
      static size_t mod55238957008387(size_t hash) { return hash % 55238957008387llu; }
      static size_t mod69596724709081(size_t hash) { return hash % 69596724709081llu; }
      static size_t mod87686378464759(size_t hash) { return hash % 87686378464759llu; }
      static size_t mod110477914016779(size_t hash) { return hash % 110477914016779llu; }
      static size_t mod139193449418173(size_t hash) { return hash % 139193449418173llu; }
      static size_t mod175372756929481(size_t hash) { return hash % 175372756929481llu; }
      static size_t mod220955828033581(size_t hash) { return hash % 220955828033581llu; }
      static size_t mod278386898836457(size_t hash) { return hash % 278386898836457llu; }
      static size_t mod350745513859007(size_t hash) { return hash % 350745513859007llu; }
      static size_t mod441911656067171(size_t hash) { return hash % 441911656067171llu; }
      static size_t mod556773797672909(size_t hash) { return hash % 556773797672909llu; }
      static size_t mod701491027718027(size_t hash) { return hash % 701491027718027llu; }
      static size_t mod883823312134381(size_t hash) { return hash % 883823312134381llu; }
      static size_t mod1113547595345903(size_t hash) { return hash % 1113547595345903llu; }
      static size_t mod1402982055436147(size_t hash) { return hash % 1402982055436147llu; }
      static size_t mod1767646624268779(size_t hash) { return hash % 1767646624268779llu; }
      static size_t mod2227095190691797(size_t hash) { return hash % 2227095190691797llu; }
      static size_t mod2805964110872297(size_t hash) { return hash % 2805964110872297llu; }
      static size_t mod3535293248537579(size_t hash) { return hash % 3535293248537579llu; }
      static size_t mod4454190381383713(size_t hash) { return hash % 4454190381383713llu; }
      static size_t mod5611928221744609(size_t hash) { return hash % 5611928221744609llu; }
      static size_t mod7070586497075177(size_t hash) { return hash % 7070586497075177llu; }
      static size_t mod8908380762767489(size_t hash) { return hash % 8908380762767489llu; }
      static size_t mod11223856443489329(size_t hash) { return hash % 11223856443489329llu; }
      static size_t mod14141172994150357(size_t hash) { return hash % 14141172994150357llu; }
      static size_t mod17816761525534927(size_t hash) { return hash % 17816761525534927llu; }
      static size_t mod22447712886978529(size_t hash) { return hash % 22447712886978529llu; }
      static size_t mod28282345988300791(size_t hash) { return hash % 28282345988300791llu; }
      static size_t mod35633523051069991(size_t hash) { return hash % 35633523051069991llu; }
      static size_t mod44895425773957261(size_t hash) { return hash % 44895425773957261llu; }
      static size_t mod56564691976601587(size_t hash) { return hash % 56564691976601587llu; }
      static size_t mod71267046102139967(size_t hash) { return hash % 71267046102139967llu; }
      static size_t mod89790851547914507(size_t hash) { return hash % 89790851547914507llu; }
      static size_t mod113129383953203213(size_t hash) { return hash % 113129383953203213llu; }
      static size_t mod142534092204280003(size_t hash) { return hash % 142534092204280003llu; }
      static size_t mod179581703095829107(size_t hash) { return hash % 179581703095829107llu; }
      static size_t mod226258767906406483(size_t hash) { return hash % 226258767906406483llu; }
      static size_t mod285068184408560057(size_t hash) { return hash % 285068184408560057llu; }
      static size_t mod359163406191658253(size_t hash) { return hash % 359163406191658253llu; }
      static size_t mod452517535812813007(size_t hash) { return hash % 452517535812813007llu; }
      static size_t mod570136368817120201(size_t hash) { return hash % 570136368817120201llu; }
      static size_t mod718326812383316683(size_t hash) { return hash % 718326812383316683llu; }
      static size_t mod905035071625626043(size_t hash) { return hash % 905035071625626043llu; }
      static size_t mod1140272737634240411(size_t hash) { return hash % 1140272737634240411llu; }
      static size_t mod1436653624766633509(size_t hash) { return hash % 1436653624766633509llu; }
      static size_t mod1810070143251252131(size_t hash) { return hash % 1810070143251252131llu; }
      static size_t mod2280545475268481167(size_t hash) { return hash % 2280545475268481167llu; }
      static size_t mod2873307249533267101(size_t hash) { return hash % 2873307249533267101llu; }
      static size_t mod3620140286502504283(size_t hash) { return hash % 3620140286502504283llu; }
      static size_t mod4561090950536962147(size_t hash) { return hash % 4561090950536962147llu; }
      static size_t mod5746614499066534157(size_t hash) { return hash % 5746614499066534157llu; }
      static size_t mod7240280573005008577(size_t hash) { return hash % 7240280573005008577llu; }
      static size_t mod9122181901073924329(size_t hash) { return hash % 9122181901073924329llu; }
      static size_t mod11493228998133068689(size_t hash) { return hash % 11493228998133068689llu; }
      static size_t mod14480561146010017169(size_t hash) { return hash % 14480561146010017169llu; }
      static size_t mod18446744073709551557(size_t hash) { return hash % 18446744073709551557llu; }
  
      using mod_function = size_t (*)(size_t);
  
      mod_function next_size_over(size_t & size) const
      {
          // prime numbers generated by the following method:
          // 1. start with a prime p = 2
          // 2. go to wolfram alpha and get p = NextPrime(2 * p)
          // 3. repeat 2. until you overflow 64 bits
          // you now have large gaps which you would hit if somebody called reserve() with an unlucky number.
          // 4. to fill the gaps for every prime p go to wolfram alpha and get ClosestPrime(p * 2^(1/3)) and ClosestPrime(p * 2^(2/3)) and put those in the gaps
          // 5. get PrevPrime(2^64) and put it at the end
          static constexpr const size_t prime_list[] =
          {
              2llu, 3llu, 5llu, 7llu, 11llu, 13llu, 17llu, 23llu, 29llu, 37llu, 47llu,
              59llu, 73llu, 97llu, 127llu, 151llu, 197llu, 251llu, 313llu, 397llu,
              499llu, 631llu, 797llu, 1009llu, 1259llu, 1597llu, 2011llu, 2539llu,
              3203llu, 4027llu, 5087llu, 6421llu, 8089llu, 10193llu, 12853llu, 16193llu,
              20399llu, 25717llu, 32401llu, 40823llu, 51437llu, 64811llu, 81649llu,
              102877llu, 129607llu, 163307llu, 205759llu, 259229llu, 326617llu,
              411527llu, 518509llu, 653267llu, 823117llu, 1037059llu, 1306601llu,
              1646237llu, 2074129llu, 2613229llu, 3292489llu, 4148279llu, 5226491llu,
              6584983llu, 8296553llu, 10453007llu, 13169977llu, 16593127llu, 20906033llu,
              26339969llu, 33186281llu, 41812097llu, 52679969llu, 66372617llu,
              83624237llu, 105359939llu, 132745199llu, 167248483llu, 210719881llu,
              265490441llu, 334496971llu, 421439783llu, 530980861llu, 668993977llu,
              842879579llu, 1061961721llu, 1337987929llu, 1685759167llu, 2123923447llu,
              2675975881llu, 3371518343llu, 4247846927llu, 5351951779llu, 6743036717llu,
              8495693897llu, 10703903591llu, 13486073473llu, 16991387857llu,
              21407807219llu, 26972146961llu, 33982775741llu, 42815614441llu,
              53944293929llu, 67965551447llu, 85631228929llu, 107888587883llu,
              135931102921llu, 171262457903llu, 215777175787llu, 271862205833llu,
              342524915839llu, 431554351609llu, 543724411781llu, 685049831731llu,
              863108703229llu, 1087448823553llu, 1370099663459llu, 1726217406467llu,
              2174897647073llu, 2740199326961llu, 3452434812973llu, 4349795294267llu,
              5480398654009llu, 6904869625999llu, 8699590588571llu, 10960797308051llu,
              13809739252051llu, 17399181177241llu, 21921594616111llu, 27619478504183llu,
              34798362354533llu, 43843189232363llu, 55238957008387llu, 69596724709081llu,
              87686378464759llu, 110477914016779llu, 139193449418173llu,
              175372756929481llu, 220955828033581llu, 278386898836457llu,
              350745513859007llu, 441911656067171llu, 556773797672909llu,
              701491027718027llu, 883823312134381llu, 1113547595345903llu,
              1402982055436147llu, 1767646624268779llu, 2227095190691797llu,
              2805964110872297llu, 3535293248537579llu, 4454190381383713llu,
              5611928221744609llu, 7070586497075177llu, 8908380762767489llu,
              11223856443489329llu, 14141172994150357llu, 17816761525534927llu,
              22447712886978529llu, 28282345988300791llu, 35633523051069991llu,
              44895425773957261llu, 56564691976601587llu, 71267046102139967llu,
              89790851547914507llu, 113129383953203213llu, 142534092204280003llu,
              179581703095829107llu, 226258767906406483llu, 285068184408560057llu,
              359163406191658253llu, 452517535812813007llu, 570136368817120201llu,
              718326812383316683llu, 905035071625626043llu, 1140272737634240411llu,
              1436653624766633509llu, 1810070143251252131llu, 2280545475268481167llu,
              2873307249533267101llu, 3620140286502504283llu, 4561090950536962147llu,
              5746614499066534157llu, 7240280573005008577llu, 9122181901073924329llu,
              11493228998133068689llu, 14480561146010017169llu, 18446744073709551557llu
          };
          static constexpr size_t (* const mod_functions[])(size_t) =
          {
              &mod0, &mod2, &mod3, &mod5, &mod7, &mod11, &mod13, &mod17, &mod23, &mod29, &mod37,
              &mod47, &mod59, &mod73, &mod97, &mod127, &mod151, &mod197, &mod251, &mod313, &mod397,
              &mod499, &mod631, &mod797, &mod1009, &mod1259, &mod1597, &mod2011, &mod2539, &mod3203,
              &mod4027, &mod5087, &mod6421, &mod8089, &mod10193, &mod12853, &mod16193, &mod20399,
              &mod25717, &mod32401, &mod40823, &mod51437, &mod64811, &mod81649, &mod102877,
              &mod129607, &mod163307, &mod205759, &mod259229, &mod326617, &mod411527, &mod518509,
              &mod653267, &mod823117, &mod1037059, &mod1306601, &mod1646237, &mod2074129,
              &mod2613229, &mod3292489, &mod4148279, &mod5226491, &mod6584983, &mod8296553,
              &mod10453007, &mod13169977, &mod16593127, &mod20906033, &mod26339969, &mod33186281,
              &mod41812097, &mod52679969, &mod66372617, &mod83624237, &mod105359939, &mod132745199,
              &mod167248483, &mod210719881, &mod265490441, &mod334496971, &mod421439783,
              &mod530980861, &mod668993977, &mod842879579, &mod1061961721, &mod1337987929,
              &mod1685759167, &mod2123923447, &mod2675975881, &mod3371518343, &mod4247846927,
              &mod5351951779, &mod6743036717, &mod8495693897, &mod10703903591, &mod13486073473,
              &mod16991387857, &mod21407807219, &mod26972146961, &mod33982775741, &mod42815614441,
              &mod53944293929, &mod67965551447, &mod85631228929, &mod107888587883, &mod135931102921,
              &mod171262457903, &mod215777175787, &mod271862205833, &mod342524915839,
              &mod431554351609, &mod543724411781, &mod685049831731, &mod863108703229,
              &mod1087448823553, &mod1370099663459, &mod1726217406467, &mod2174897647073,
              &mod2740199326961, &mod3452434812973, &mod4349795294267, &mod5480398654009,
              &mod6904869625999, &mod8699590588571, &mod10960797308051, &mod13809739252051,
              &mod17399181177241, &mod21921594616111, &mod27619478504183, &mod34798362354533,
              &mod43843189232363, &mod55238957008387, &mod69596724709081, &mod87686378464759,
              &mod110477914016779, &mod139193449418173, &mod175372756929481, &mod220955828033581,
              &mod278386898836457, &mod350745513859007, &mod441911656067171, &mod556773797672909,
              &mod701491027718027, &mod883823312134381, &mod1113547595345903, &mod1402982055436147,
              &mod1767646624268779, &mod2227095190691797, &mod2805964110872297, &mod3535293248537579,
              &mod4454190381383713, &mod5611928221744609, &mod7070586497075177, &mod8908380762767489,
              &mod11223856443489329, &mod14141172994150357, &mod17816761525534927,
              &mod22447712886978529, &mod28282345988300791, &mod35633523051069991,
              &mod44895425773957261, &mod56564691976601587, &mod71267046102139967,
              &mod89790851547914507, &mod113129383953203213, &mod142534092204280003,
              &mod179581703095829107, &mod226258767906406483, &mod285068184408560057,
              &mod359163406191658253, &mod452517535812813007, &mod570136368817120201,
              &mod718326812383316683, &mod905035071625626043, &mod1140272737634240411,
              &mod1436653624766633509, &mod1810070143251252131, &mod2280545475268481167,
              &mod2873307249533267101, &mod3620140286502504283, &mod4561090950536962147,
              &mod5746614499066534157, &mod7240280573005008577, &mod9122181901073924329,
              &mod11493228998133068689, &mod14480561146010017169, &mod18446744073709551557
          };
          const size_t * found = std::lower_bound(std::begin(prime_list), std::end(prime_list) - 1, size);
          size = *found;
          return mod_functions[1 + found - prime_list];
      }
      void commit(mod_function new_mod_function)
      {
          current_mod_function = new_mod_function;
      }
      void reset()
      {
          current_mod_function = &mod0;
      }
  
      size_t index_for_hash(size_t hash, size_t /*num_slots_minus_one*/) const
      {
          return current_mod_function(hash);
      }
      size_t keep_in_range(size_t index, size_t num_slots_minus_one) const
      {
          return index > num_slots_minus_one ? current_mod_function(index) : index;
      }
  
  private:
      mod_function current_mod_function = &mod0;
  };
  
  struct power_of_two_hash_policy
  {
      size_t index_for_hash(size_t hash, size_t num_slots_minus_one) const
      {
          return hash & num_slots_minus_one;
      }
      size_t keep_in_range(size_t index, size_t num_slots_minus_one) const
      {
          return index_for_hash(index, num_slots_minus_one);
      }
      int8_t next_size_over(size_t & size) const
      {
          size = detailv3::next_power_of_two(size);
          return 0;
      }
      void commit(int8_t)
      {
      }
      void reset()
      {
      }
  
  };
  
  struct fibonacci_hash_policy
  {
      size_t index_for_hash(size_t hash, size_t /*num_slots_minus_one*/) const
      {
          return (11400714819323198485ull * hash) >> shift;
      }
      size_t keep_in_range(size_t index, size_t num_slots_minus_one) const
      {
          return index & num_slots_minus_one;
      }
  
      int8_t next_size_over(size_t & size) const
      {
          size = std::max(size_t(2), detailv3::next_power_of_two(size));
          return 64 - detailv3::log2(size);
      }
      void commit(int8_t shift)
      {
          this->shift = shift;
      }
      void reset()
      {
          shift = 63;
      }
  
  private:
      int8_t shift = 63;
  };
  
  template<typename K, typename V, typename H = std::hash<K>, typename E = std::equal_to<K>, typename A = std::allocator<std::pair<K, V> > >
  class flat_hash_map
          : public detailv3::sherwood_v3_table
          <
              std::pair<K, V>,
              K,
              H,
              detailv3::KeyOrValueHasher<K, std::pair<K, V>, H>,
              E,
              detailv3::KeyOrValueEquality<K, std::pair<K, V>, E>,
              A,
              typename std::allocator_traits<A>::template rebind_alloc<detailv3::sherwood_v3_entry<std::pair<K, V>>>
          >
  {
      using Table = detailv3::sherwood_v3_table
      <
          std::pair<K, V>,
          K,
          H,
          detailv3::KeyOrValueHasher<K, std::pair<K, V>, H>,
          E,
          detailv3::KeyOrValueEquality<K, std::pair<K, V>, E>,
          A,
          typename std::allocator_traits<A>::template rebind_alloc<detailv3::sherwood_v3_entry<std::pair<K, V>>>
      >;
  public:
  
      using key_type = K;
      using mapped_type = V;
  
      using Table::Table;
      flat_hash_map()
      {
      }
  
      inline V & operator[](const K & key)
      {
          return emplace(key, convertible_to_value()).first->second;
      }
      inline V & operator[](K && key)
      {
          return emplace(std::move(key), convertible_to_value()).first->second;
      }
      V & at(const K & key)
      {
          auto found = this->find(key);
          if (found == this->end())
              throw std::out_of_range("Argument passed to at() was not in the map.");
          return found->second;
      }
      const V & at(const K & key) const
      {
          auto found = this->find(key);
          if (found == this->end())
              throw std::out_of_range("Argument passed to at() was not in the map.");
          return found->second;
      }
  
      using Table::emplace;
      std::pair<typename Table::iterator, bool> emplace()
      {
          return emplace(key_type(), convertible_to_value());
      }
      template<typename M>
      std::pair<typename Table::iterator, bool> insert_or_assign(const key_type & key, M && m)
      {
          auto emplace_result = emplace(key, std::forward<M>(m));
          if (!emplace_result.second)
              emplace_result.first->second = std::forward<M>(m);
          return emplace_result;
      }
      template<typename M>
      std::pair<typename Table::iterator, bool> insert_or_assign(key_type && key, M && m)
      {
          auto emplace_result = emplace(std::move(key), std::forward<M>(m));
          if (!emplace_result.second)
              emplace_result.first->second = std::forward<M>(m);
          return emplace_result;
      }
      template<typename M>
      typename Table::iterator insert_or_assign(typename Table::const_iterator, const key_type & key, M && m)
      {
          return insert_or_assign(key, std::forward<M>(m)).first;
      }
      template<typename M>
      typename Table::iterator insert_or_assign(typename Table::const_iterator, key_type && key, M && m)
      {
          return insert_or_assign(std::move(key), std::forward<M>(m)).first;
      }
  
      friend bool operator==(const flat_hash_map & lhs, const flat_hash_map & rhs)
      {
          if (lhs.size() != rhs.size())
              return false;
          for (const typename Table::value_type & value : lhs)
          {
              auto found = rhs.find(value.first);
              if (found == rhs.end())
                  return false;
              else if (value.second != found->second)
                  return false;
          }
          return true;
      }
      friend bool operator!=(const flat_hash_map & lhs, const flat_hash_map & rhs)
      {
          return !(lhs == rhs);
      }
  
  private:
      struct convertible_to_value
      {
          operator V() const
          {
              return V();
          }
      };
  };
  
  template<typename T, typename H = std::hash<T>, typename E = std::equal_to<T>, typename A = std::allocator<T> >
  class flat_hash_set
          : public detailv3::sherwood_v3_table
          <
              T,
              T,
              H,
              detailv3::functor_storage<size_t, H>,
              E,
              detailv3::functor_storage<bool, E>,
              A,
              typename std::allocator_traits<A>::template rebind_alloc<detailv3::sherwood_v3_entry<T>>
          >
  {
      using Table = detailv3::sherwood_v3_table
      <
          T,
          T,
          H,
          detailv3::functor_storage<size_t, H>,
          E,
          detailv3::functor_storage<bool, E>,
          A,
          typename std::allocator_traits<A>::template rebind_alloc<detailv3::sherwood_v3_entry<T>>
      >;
  public:
  
      using key_type = T;
  
      using Table::Table;
      flat_hash_set()
      {
      }
  
      template<typename... Args>
      std::pair<typename Table::iterator, bool> emplace(Args &&... args)
      {
          return Table::emplace(T(std::forward<Args>(args)...));
      }
      std::pair<typename Table::iterator, bool> emplace(const key_type & arg)
      {
          return Table::emplace(arg);
      }
      std::pair<typename Table::iterator, bool> emplace(key_type & arg)
      {
          return Table::emplace(arg);
      }
      std::pair<typename Table::iterator, bool> emplace(const key_type && arg)
      {
          return Table::emplace(std::move(arg));
      }
      std::pair<typename Table::iterator, bool> emplace(key_type && arg)
      {
          return Table::emplace(std::move(arg));
      }
  
      friend bool operator==(const flat_hash_set & lhs, const flat_hash_set & rhs)
      {
          if (lhs.size() != rhs.size())
              return false;
          for (const T & value : lhs)
          {
              if (rhs.find(value) == rhs.end())
                  return false;
          }
          return true;
      }
      friend bool operator!=(const flat_hash_set & lhs, const flat_hash_set & rhs)
      {
          return !(lhs == rhs);
      }
  };
  
  
  template<typename T>
  struct power_of_two_std_hash : std::hash<T>
  {
      typedef ska::power_of_two_hash_policy hash_policy;
  };
  
  } // end namespace ska
  