resize_policy.hpp

Go to the documentation of this file.

// -*- C++ -*-
 
// Copyright (C) 2005-2021 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/>.
 
// Copyright (C) 2004 Ami Tavory and Vladimir Dreizin, IBM-HRL.
 
// 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 binary_heap_/resize_policy.hpp
 * Contains an implementation class for a binary_heap.
 */
 
#ifndef PB_DS_BINARY_HEAP_RESIZE_POLICY_HPP
#define PB_DS_BINARY_HEAP_RESIZE_POLICY_HPP
 
#include <debug/debug.h>
 
namespace __gnu_pbds
{
  namespace detail
  {
    /// Resize policy for binary heap.
    template<typename _Tp>
    class resize_policy
    {
    private:
      enum
        {
          ratio = 8,
          factor = 2
        };
 
      /// Next shrink size.
      _Tp               m_shrink_size;
 
      /// Next grow size.
      _Tp               m_grow_size;
 
    public:
      typedef _Tp       size_type;
 
      static const _Tp  min_size = 16;
 
      resize_policy() : m_shrink_size(0), m_grow_size(min_size)
      { PB_DS_ASSERT_VALID((*this)) }
 
      resize_policy(const resize_policy& other)
      : m_shrink_size(other.m_shrink_size), m_grow_size(other.m_grow_size)
      { PB_DS_ASSERT_VALID((*this)) }
 
      inline void
      swap(resize_policy<_Tp>&);
 
      inline bool
      resize_needed_for_grow(size_type) const;
 
      inline bool
      resize_needed_for_shrink(size_type) const;
 
      inline bool
      grow_needed(size_type) const;
 
      inline bool
      shrink_needed(size_type) const;
 
      inline size_type
      get_new_size_for_grow() const;
 
      inline size_type
      get_new_size_for_shrink() const;
 
      inline size_type
      get_new_size_for_arbitrary(size_type) const;
 
      inline void
      notify_grow_resize();
 
      inline void
      notify_shrink_resize();
 
      void
      notify_arbitrary(size_type);
 
#ifdef _GLIBCXX_DEBUG
      void
      assert_valid(const char*, int) const;
#endif
 
#ifdef PB_DS_BINARY_HEAP_TRACE_
      void
      trace() const;
#endif
    };
 
    template<typename _Tp>
      const _Tp resize_policy<_Tp>::min_size;
 
    template<typename _Tp>
    inline void
    resize_policy<_Tp>::
    swap(resize_policy<_Tp>& other)
    {
      std::swap(m_shrink_size, other.m_shrink_size);
      std::swap(m_grow_size, other.m_grow_size);
    }
 
    template<typename _Tp>
    inline bool
    resize_policy<_Tp>::
    resize_needed_for_grow(size_type size) const
    {
      _GLIBCXX_DEBUG_ASSERT(size <= m_grow_size);
      return size == m_grow_size;
    }
 
    template<typename _Tp>
    inline bool
    resize_policy<_Tp>::
    resize_needed_for_shrink(size_type size) const
    {
      _GLIBCXX_DEBUG_ASSERT(size <= m_grow_size);
      return size == m_shrink_size;
    }
 
    template<typename _Tp>
    inline typename resize_policy<_Tp>::size_type
    resize_policy<_Tp>::
    get_new_size_for_grow() const
    { return m_grow_size * factor; }
 
    template<typename _Tp>
    inline typename resize_policy<_Tp>::size_type
    resize_policy<_Tp>::
    get_new_size_for_shrink() const
    {
      const size_type half_size = m_grow_size / factor;
      return std::max(min_size, half_size);
    }
 
    template<typename _Tp>
    inline typename resize_policy<_Tp>::size_type
    resize_policy<_Tp>::
    get_new_size_for_arbitrary(size_type size) const
    {
      size_type ret = min_size;
      while (ret < size)
        ret *= factor;
      return ret;
    }
 
    template<typename _Tp>
    inline void
    resize_policy<_Tp>::
    notify_grow_resize()
    {
      PB_DS_ASSERT_VALID((*this))
      _GLIBCXX_DEBUG_ASSERT(m_grow_size >= min_size);
      m_grow_size *= factor;
      m_shrink_size = m_grow_size / ratio;
      PB_DS_ASSERT_VALID((*this))
    }
 
    template<typename _Tp>
    inline void
    resize_policy<_Tp>::
    notify_shrink_resize()
    {
      PB_DS_ASSERT_VALID((*this))
      m_shrink_size /= factor;
      if (m_shrink_size == 1)
        m_shrink_size = 0;
      m_grow_size = std::max(m_grow_size / factor, min_size);
      PB_DS_ASSERT_VALID((*this))
    }
 
    template<typename _Tp>
    inline void
    resize_policy<_Tp>::
    notify_arbitrary(size_type actual_size)
    {
      m_grow_size = actual_size;
      m_shrink_size = m_grow_size / ratio;
      PB_DS_ASSERT_VALID((*this))
    }
 
#ifdef _GLIBCXX_DEBUG
    template<typename _Tp>
    void
    resize_policy<_Tp>::
    assert_valid(const char* __file, int __line) const
    {
      PB_DS_DEBUG_VERIFY(m_shrink_size == 0
                         || m_shrink_size * ratio == m_grow_size);
      PB_DS_DEBUG_VERIFY(m_grow_size >= min_size);
    }
#endif
 
#ifdef PB_DS_BINARY_HEAP_TRACE_
    template<typename _Tp>
    void
    resize_policy<_Tp>::
    trace() const
    {
      std::cerr << "shrink = " << m_shrink_size
                << " grow = " << m_grow_size << std::endl;
    }
#endif
 
} // namespace detail
} // namespace __gnu_pbds
 
#endif