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editing: hash_policy.hpp

// -*- C++ -*-

// Copyright (C) 2005-2024 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the terms
// of the GNU General Public License as published by the Free Software
// Foundation; either version 3, or (at your option) any later
// version.

// This library is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// General Public License for more details.

// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.

// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
// <http://www.gnu.org/licenses/>.

// Permission to use, copy, modify, sell, and distribute this software
// is hereby granted without fee, provided that the above copyright
// notice appears in all copies, and that both that copyright notice
// and this permission notice appear in supporting documentation. None
// of the above authors, nor IBM Haifa Research Laboratories, make any
// representation about the suitability of this software for any
// purpose. It is provided "as is" without express or implied
// warranty.

/**
 * @file hash_policy.hpp
 * Contains hash-related policies.
 */

#ifndef PB_DS_HASH_POLICY_HPP
#define PB_DS_HASH_POLICY_HPP

#include <bits/c++config.h>
#include <algorithm>
#include <vector>
#include <cmath>
#include <ext/pb_ds/exception.hpp>
#include <ext/pb_ds/detail/type_utils.hpp>
#include <ext/pb_ds/detail/hash_fn/mask_based_range_hashing.hpp>
#include <ext/pb_ds/detail/hash_fn/mod_based_range_hashing.hpp>
#include <ext/pb_ds/detail/resize_policy/hash_load_check_resize_trigger_size_base.hpp>

namespace __gnu_pbds
{
#define PB_DS_CLASS_T_DEC template<typename Size_Type>
#define PB_DS_CLASS_C_DEC linear_probe_fn<Size_Type>

/// A probe sequence policy using fixed increments.
  template<typename Size_Type = std::size_t>
  class linear_probe_fn
  {
  public:
    typedef Size_Type size_type;

void
    swap(PB_DS_CLASS_C_DEC& other);

protected:
    /// Returns the i-th offset from the hash value.
    inline size_type
    operator()(size_type i) const;
  };

#include <ext/pb_ds/detail/hash_fn/linear_probe_fn_imp.hpp>

#undef PB_DS_CLASS_T_DEC
#undef PB_DS_CLASS_C_DEC

#define PB_DS_CLASS_T_DEC template<typename Size_Type>
#define PB_DS_CLASS_C_DEC quadratic_probe_fn<Size_Type>

/// A probe sequence policy using square increments.
  template<typename Size_Type = std::size_t>
  class quadratic_probe_fn
  {
  public:
    typedef Size_Type size_type;

void
    swap(PB_DS_CLASS_C_DEC& other);

protected:
    /// Returns the i-th offset from the hash value.
    inline size_type
    operator()(size_type i) const;
  };

#include <ext/pb_ds/detail/hash_fn/quadratic_probe_fn_imp.hpp>

#undef PB_DS_CLASS_T_DEC
#undef PB_DS_CLASS_C_DEC

#define PB_DS_CLASS_T_DEC template<typename Size_Type>
#define PB_DS_CLASS_C_DEC direct_mask_range_hashing<Size_Type>

/// A mask range-hashing class (uses a bitmask).
  template<typename Size_Type = std::size_t>
  class direct_mask_range_hashing
  : public detail::mask_based_range_hashing<Size_Type>
  {
  private:
    typedef detail::mask_based_range_hashing<Size_Type> mask_based_base;

public:
    typedef Size_Type size_type;

void
    swap(PB_DS_CLASS_C_DEC& other);

protected:
    void
    notify_resized(size_type size);

/// Transforms the __hash value hash into a ranged-hash value
    /// (using a bit-mask).
    inline size_type
    operator()(size_type hash) const;
  };

#include <ext/pb_ds/detail/hash_fn/direct_mask_range_hashing_imp.hpp>

#undef PB_DS_CLASS_T_DEC
#undef PB_DS_CLASS_C_DEC

#define PB_DS_CLASS_T_DEC template<typename Size_Type>
#define PB_DS_CLASS_C_DEC direct_mod_range_hashing<Size_Type>

/// A mod range-hashing class (uses the modulo function).
  template<typename Size_Type = std::size_t>
  class direct_mod_range_hashing
  : public detail::mod_based_range_hashing<Size_Type>
  {
  public:
    typedef Size_Type size_type;

void
    swap(PB_DS_CLASS_C_DEC& other);

protected:
    void
    notify_resized(size_type size);

/// Transforms the __hash value hash into a ranged-hash value
    /// (using a modulo operation).
    inline size_type
    operator()(size_type hash) const;

private:
    typedef detail::mod_based_range_hashing<size_type> mod_based_base;
  };

#include <ext/pb_ds/detail/hash_fn/direct_mod_range_hashing_imp.hpp>

#undef PB_DS_CLASS_T_DEC
#undef PB_DS_CLASS_C_DEC

#define PB_DS_CLASS_T_DEC template<bool External_Load_Access, typename Size_Type>
#define PB_DS_CLASS_C_DEC hash_load_check_resize_trigger<External_Load_Access, Size_Type>
#define PB_DS_SIZE_BASE_C_DEC detail::hash_load_check_resize_trigger_size_base<Size_Type, External_Load_Access>

/// A resize trigger policy based on a load check. It keeps the
  /// load factor between some load factors load_min and load_max.
  template<bool External_Load_Access = false, typename Size_Type = std::size_t>
  class hash_load_check_resize_trigger : private PB_DS_SIZE_BASE_C_DEC
  {
  public:
    typedef Size_Type size_type;

enum
      {
	/// Specifies whether the load factor can be accessed
	/// externally. The two options have different trade-offs in
	/// terms of flexibility, genericity, and encapsulation.
	external_load_access = External_Load_Access
      };

/// Default constructor, or constructor taking load_min and
    /// load_max load factors between which this policy will keep the
    /// actual load.
    hash_load_check_resize_trigger(float load_min = 0.125,
				   float load_max = 0.5);

void
    swap(hash_load_check_resize_trigger& other);

virtual
    ~hash_load_check_resize_trigger();

/// Returns a pair of the minimal and maximal loads, respectively.
    inline std::pair<float, float>
    get_loads() const;

/// Sets the loads through a pair of the minimal and maximal
    /// loads, respectively.
    void
    set_loads(std::pair<float, float> load_pair);

protected:
    inline void
    notify_insert_search_start();

inline void
    notify_insert_search_collision();

inline void
    notify_insert_search_end();

inline void
    notify_find_search_start();

inline void
    notify_find_search_collision();

inline void
    notify_find_search_end();

inline void
    notify_erase_search_start();

inline void
    notify_erase_search_collision();

inline void
    notify_erase_search_end();

/// Notifies an element was inserted. The total number of entries
    /// in the table is num_entries.
    inline void
    notify_inserted(size_type num_entries);

inline void
    notify_erased(size_type num_entries);

/// Notifies the table was cleared.
    void
    notify_cleared();

/// Notifies the table was resized as a result of this object's
    /// signifying that a resize is needed.
    void
    notify_resized(size_type new_size);

void
    notify_externally_resized(size_type new_size);

inline bool
    is_resize_needed() const;

inline bool
    is_grow_needed(size_type size, size_type num_entries) const;

private:
    virtual void
    do_resize(size_type new_size);

typedef PB_DS_SIZE_BASE_C_DEC size_base;

#ifdef _GLIBCXX_DEBUG
    void
    assert_valid(const char* file, int line) const;
#endif

float 	m_load_min;
    float 	m_load_max;
    size_type 	m_next_shrink_size;
    size_type 	m_next_grow_size;
    bool 	m_resize_needed;
  };

#include <ext/pb_ds/detail/resize_policy/hash_load_check_resize_trigger_imp.hpp>

#undef PB_DS_CLASS_T_DEC
#undef PB_DS_CLASS_C_DEC
#undef PB_DS_SIZE_BASE_C_DEC

#define PB_DS_CLASS_T_DEC template<bool External_Load_Access, typename Size_Type>
#define PB_DS_CLASS_C_DEC cc_hash_max_collision_check_resize_trigger<External_Load_Access, Size_Type>

/// A resize trigger policy based on collision checks. It keeps the
  /// simulated load factor lower than some given load factor.
  template<bool External_Load_Access = false, typename Size_Type = std::size_t>
  class cc_hash_max_collision_check_resize_trigger
  {
  public:
    typedef Size_Type 	size_type;

/// Default constructor, or constructor taking load, a __load
    /// factor which it will attempt to maintain.
    cc_hash_max_collision_check_resize_trigger(float load = 0.5);

void
    swap(PB_DS_CLASS_C_DEC& other);

/// Returns the current load.
    inline float
    get_load() const;

/// Sets the load; does not resize the container.
    void
    set_load(float load);

protected:
    /// Notifies an insert search started.
    inline void
    notify_insert_search_start();

/// Notifies a search encountered a collision.
    inline void
    notify_insert_search_collision();

/// Notifies a search ended.
    inline void
    notify_insert_search_end();

/// Notifies a find search started.
    inline void
    notify_find_search_start();

/// Notifies a search encountered a collision.
    inline void
    notify_find_search_collision();

/// Notifies a search ended.
    inline void
    notify_find_search_end();

/// Notifies an erase search started.
    inline void
    notify_erase_search_start();

/// Notifies a search encountered a collision.
    inline void
    notify_erase_search_collision();

/// Notifies a search ended.
    inline void
    notify_erase_search_end();

/// Notifies an element was inserted.
    inline void
    notify_inserted(size_type num_entries);

/// Notifies an element was erased.
    inline void
    notify_erased(size_type num_entries);

/// Notifies the table was cleared.
    void
    notify_cleared();

/// Notifies the table was resized as a result of this object's
    /// signifying that a resize is needed.
    void
    notify_resized(size_type new_size);

/// Notifies the table was resized externally.
    void
    notify_externally_resized(size_type new_size);

/// Queries whether a resize is needed.
    inline bool
    is_resize_needed() const;

/// Queries whether a grow is needed. This method is called only
    /// if this object indicated is needed.
    inline bool
    is_grow_needed(size_type size, size_type num_entries) const;

private:
    void
    calc_max_num_coll();

inline void
    calc_resize_needed();

float 	m_load;
    size_type 	m_size;
    size_type 	m_num_col;
    size_type 	m_max_col;
    bool 	m_resize_needed;
  };

#include <ext/pb_ds/detail/resize_policy/cc_hash_max_collision_check_resize_trigger_imp.hpp>

#undef PB_DS_CLASS_T_DEC
#undef PB_DS_CLASS_C_DEC

#define PB_DS_CLASS_T_DEC template<typename Size_Type>
#define PB_DS_CLASS_C_DEC hash_exponential_size_policy<Size_Type>

/// A size policy whose sequence of sizes form an exponential
  /// sequence (typically powers of 2.
  template<typename Size_Type = std::size_t>
  class hash_exponential_size_policy
  {
  public:
    typedef Size_Type size_type;

/// Default constructor, or onstructor taking a start_size, or
    /// constructor taking a start size and grow_factor. The policy
    /// will use the sequence of sizes start_size, start_size*
    /// grow_factor, start_size* grow_factor^2, ...
    hash_exponential_size_policy(size_type start_size = 8,
				 size_type grow_factor = 2);

void
    swap(PB_DS_CLASS_C_DEC& other);

protected:
    size_type
    get_nearest_larger_size(size_type size) const;

size_type
    get_nearest_smaller_size(size_type size) const;

private:
    size_type m_start_size;
    size_type m_grow_factor;
  };

#include <ext/pb_ds/detail/resize_policy/hash_exponential_size_policy_imp.hpp>

#undef PB_DS_CLASS_T_DEC
#undef PB_DS_CLASS_C_DEC

#define PB_DS_CLASS_T_DEC
#define PB_DS_CLASS_C_DEC hash_prime_size_policy

/// A size policy whose sequence of sizes form a nearly-exponential
  /// sequence of primes.
  class hash_prime_size_policy
  {
  public:
    /// Size type.
    typedef std::size_t size_type;

/// Default constructor, or onstructor taking a start_size The
    /// policy will use the sequence of sizes approximately
    /// start_size, start_size* 2, start_size* 2^2, ...
    hash_prime_size_policy(size_type start_size = 8);

inline void
    swap(PB_DS_CLASS_C_DEC& other);

protected:
    size_type
    get_nearest_larger_size(size_type size) const;

size_type
    get_nearest_smaller_size(size_type size) const;

private:
    size_type m_start_size;
  };

#include <ext/pb_ds/detail/resize_policy/hash_prime_size_policy_imp.hpp>

#undef PB_DS_CLASS_T_DEC
#undef PB_DS_CLASS_C_DEC

#define PB_DS_CLASS_T_DEC template<typename Size_Policy, typename Trigger_Policy, bool External_Size_Access, typename Size_Type>

#define PB_DS_CLASS_C_DEC hash_standard_resize_policy<Size_Policy, Trigger_Policy, External_Size_Access, Size_Type>

/// A resize policy which delegates operations to size and trigger policies.
  template<typename Size_Policy = hash_exponential_size_policy<>,
	   typename Trigger_Policy = hash_load_check_resize_trigger<>,
	   bool External_Size_Access = false,
	   typename Size_Type = std::size_t>
  class hash_standard_resize_policy
  : public Size_Policy, public Trigger_Policy
  {
  public:
    typedef Size_Type 		size_type;
    typedef Trigger_Policy 	trigger_policy;
    typedef Size_Policy 	size_policy;

enum
      {
	external_size_access = External_Size_Access
      };

/// Default constructor.
    hash_standard_resize_policy();

/// constructor taking some policies r_size_policy will be copied
    /// by the Size_Policy object of this object.
    hash_standard_resize_policy(const Size_Policy& r_size_policy);

/// constructor taking some policies. r_size_policy will be
    /// copied by the Size_Policy object of this
    /// object. r_trigger_policy will be copied by the Trigger_Policy
    /// object of this object.
    hash_standard_resize_policy(const Size_Policy& r_size_policy,
				const Trigger_Policy& r_trigger_policy);

virtual
    ~hash_standard_resize_policy();

inline void
    swap(PB_DS_CLASS_C_DEC& other);

/// Access to the Size_Policy object used.
    Size_Policy&
    get_size_policy();

/// Const access to the Size_Policy object used.
    const Size_Policy&
    get_size_policy() const;

/// Access to the Trigger_Policy object used.
    Trigger_Policy&
    get_trigger_policy();

/// Access to the Trigger_Policy object used.
    const Trigger_Policy&
    get_trigger_policy() const;

/// Returns the actual size of the container.
    inline size_type
    get_actual_size() const;

/// Resizes the container to suggested_new_size, a suggested size
    /// (the actual size will be determined by the Size_Policy
    /// object).
    void
    resize(size_type suggested_new_size);

protected:
    inline void
    notify_insert_search_start();

inline void
    notify_insert_search_collision();

inline void
    notify_insert_search_end();

inline void
    notify_find_search_start();

inline void
    notify_find_search_collision();

inline void
    notify_find_search_end();

inline void
    notify_erase_search_start();

inline void
    notify_erase_search_collision();

inline void
    notify_erase_search_end();

inline void
    notify_inserted(size_type num_e);

inline void
    notify_erased(size_type num_e);

void
    notify_cleared();

void
    notify_resized(size_type new_size);

inline bool
    is_resize_needed() const;

/// Queries what the new size should be, when the container is
    /// resized naturally. The current __size of the container is
    /// size, and the number of used entries within the container is
    /// num_used_e.
    size_type
    get_new_size(size_type size, size_type num_used_e) const;

private:
    /// Resizes to new_size.
    virtual void
    do_resize(size_type new_size);

typedef Trigger_Policy trigger_policy_base;

typedef Size_Policy size_policy_base;

size_type m_size;
  };

#include <ext/pb_ds/detail/resize_policy/hash_standard_resize_policy_imp.hpp>

#undef PB_DS_CLASS_T_DEC
#undef PB_DS_CLASS_C_DEC

} // namespace __gnu_pbds

#endif

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