resize_policy.hpp

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// -*- C++ -*-

// Copyright (C) 2005-2019 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
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// 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