resize_policy.hpp
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// -*- C++ -*-
// Copyright (C) 2005-2026 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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/**
* @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
debug.h
std::max
constexpr const _Tp & max(const _Tp &, const _Tp &)
This does what you think it does.
Definition stl_algobase.h:256
std::endl
basic_ostream< _CharT, _Traits > & endl(basic_ostream< _CharT, _Traits > &__os)
Write a newline and flush the stream.
Definition ostream:71
std::cerr
ostream cerr
Linked to standard error (unbuffered).
__gnu_pbds
GNU extensions for policy-based data structures for public use.
Definition assoc_container.hpp:52
__gnu_pbds::detail::size_type
__gnu_pbds::detail::resize_policy
Resize policy for binary heap.
Definition resize_policy.hpp:53