// -*- C++ -*-
// Copyright (C) 2007, 2008, 2009 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/>.
/** @file parallel/losertree.h
* @brief Many generic loser tree variants.
* This file is a GNU parallel extension to the Standard C++ Library.
*/
// Written by Johannes Singler.
#ifndef _GLIBCXX_PARALLEL_LOSERTREE_H
#define _GLIBCXX_PARALLEL_LOSERTREE_H 1
#include <functional>
#include <bits/stl_algobase.h>
#include <parallel/features.h>
#include <parallel/base.h>
namespace __gnu_parallel
{
/**
* @brief Guarded loser/tournament tree.
*
* The smallest element is at the top.
*
* Guarding is done explicitly through one flag sup per element,
* inf is not needed due to a better initialization routine. This
* is a well-performing variant.
*
* @param T the element type
* @param Comparator the comparator to use, defaults to std::less<T>
*/
template<typename T, typename Comparator>
class LoserTreeBase
{
protected:
/** @brief Internal representation of a LoserTree element. */
struct Loser
{
/** @brief flag, true iff this is a "maximum" sentinel. */
bool sup;
/** @brief index of the source sequence. */
int source;
/** @brief key of the element in the LoserTree. */
T key;
};
unsigned int ik, k, offset;
/** log_2{k} */
unsigned int _M_log_k;
/** @brief LoserTree elements. */
Loser* losers;
/** @brief Comparator to use. */
Comparator comp;
/**
* @brief State flag that determines whether the LoserTree is empty.
*
* Only used for building the LoserTree.
*/
bool first_insert;
public:
/**
* @brief The constructor.
*
* @param _k The number of sequences to merge.
* @param _comp The comparator to use.
*/
LoserTreeBase(unsigned int _k, Comparator _comp)
: comp(_comp)
{
ik = _k;
// Compute log_2{k} for the Loser Tree
_M_log_k = __log2(ik - 1) + 1;
// Next greater power of 2.
k = 1 << _M_log_k;
offset = k;
// Avoid default-constructing losers[].key
losers = static_cast<Loser*>(::operator new(2 * k * sizeof(Loser)));
for (unsigned int i = ik - 1; i < k; ++i)
losers[i + k].sup = true;
first_insert = true;
}
/**
* @brief The destructor.
*/
~LoserTreeBase()
{ ::operator delete(losers); }
/**
* @brief Initializes the sequence "source" with the element "key".
*
* @param key the element to insert
* @param source index of the source sequence
* @param sup flag that determines whether the value to insert is an
* explicit supremum.
*/
inline void
insert_start(const T& key, int source, bool sup)
{
unsigned int pos = k + source;
if(first_insert)
{
// Construct all keys, so we can easily deconstruct them.
for (unsigned int i = 0; i < (2 * k); ++i)
new(&(losers[i].key)) T(key);
first_insert = false;
}
else
new(&(losers[pos].key)) T(key);
losers[pos].sup = sup;
losers[pos].source = source;
}
/**
* @return the index of the sequence with the smallest element.
*/
int get_min_source()
{ return losers[0].source; }
};
/**
* @brief Stable LoserTree variant.
*
* Provides the stable implementations of insert_start, init_winner,
* init and delete_min_insert.
*
* Unstable variant is done using partial specialisation below.
*/
template<bool stable/* default == true */, typename T, typename Comparator>
class LoserTree : public LoserTreeBase<T, Comparator>
{
typedef LoserTreeBase<T, Comparator> Base;
using Base::k;
using Base::losers;
using Base::first_insert;
public:
LoserTree(unsigned int _k, Comparator _comp)
: Base::LoserTreeBase(_k, _comp)
{}
unsigned int
init_winner(unsigned int root)
{
if (root >= k)
{
return root;
}
else
{
unsigned int left = init_winner (2 * root);
unsigned int right = init_winner (2 * root + 1);
if (losers[right].sup
|| (!losers[left].sup
&& !comp(losers[right].key, losers[left].key)))
{
// Left one is less or equal.
losers[root] = losers[right];
return left;
}
else
{
// Right one is less.
losers[root] = losers[left];
return right;
}
}
}
void init()
{ losers[0] = losers[init_winner(1)]; }
/**
* @brief Delete the smallest element and insert a new element from
* the previously smallest element's sequence.
*
* This implementation is stable.
*/
// Do not pass a const reference since key will be used as local variable.
void delete_min_insert(T key, bool sup)
{
#if _GLIBCXX_ASSERTIONS
// no dummy sequence can ever be at the top!
_GLIBCXX_PARALLEL_ASSERT(losers[0].source != -1);
#endif
int source = losers[0].source;
for (unsigned int pos = (k + source) / 2; pos > 0; pos /= 2)
{
// The smaller one gets promoted, ties are broken by source.
if ((sup && (!losers[pos].sup || losers[pos].source < source))
|| (!sup && !losers[pos].sup
&& ((comp(losers[pos].key, key))
|| (!comp(key, losers[pos].key)
&& losers[pos].source < source))))
{
// The other one is smaller.
std::swap(losers[pos].sup, sup);
std::swap(losers[pos].source, source);
std::swap(losers[pos].key, key);
}
}
losers[0].sup = sup;
losers[0].source = source;
losers[0].key = key;
}
};
/**
* @brief Unstable LoserTree variant.
*
* Stability (non-stable here) is selected with partial specialization.
*/
template<typename T, typename Comparator>
class LoserTree</* stable == */false, T, Comparator> :
public LoserTreeBase<T, Comparator>
{
typedef LoserTreeBase<T, Comparator> Base;
using Base::_M_log_k;
using Base::k;
using Base::losers;
using Base::first_insert;
public:
LoserTree(unsigned int _k, Comparator _comp)
: Base::LoserTreeBase(_k, _comp)
{}
/**
* Computes the winner of the competition at position "root".
*
* Called recursively (starting at 0) to build the initial tree.
*
* @param root index of the "game" to start.
*/
unsigned int
init_winner (unsigned int root)
{
if (root >= k)
{
return root;
}
else
{
unsigned int left = init_winner (2 * root);
unsigned int right = init_winner (2 * root + 1);
if (losers[right].sup ||
(!losers[left].sup
&& !comp(losers[right].key, losers[left].key)))
{
// Left one is less or equal.
losers[root] = losers[right];
return left;
}
else
{
// Right one is less.
losers[root] = losers[left];
return right;
}
}
}
inline void
init()
{ losers[0] = losers[init_winner(1)]; }
/**
* Delete the key smallest element and insert the element key instead.
*
* @param key the key to insert
* @param sup true iff key is an explicitly marked supremum
*/
// Do not pass a const reference since key will be used as local variable.
inline void
delete_min_insert(T key, bool sup)
{
#if _GLIBCXX_ASSERTIONS
// no dummy sequence can ever be at the top!
_GLIBCXX_PARALLEL_ASSERT(losers[0].source != -1);
#endif
int source = losers[0].source;
for (unsigned int pos = (k + source) / 2; pos > 0; pos /= 2)
{
// The smaller one gets promoted.
if (sup || (!losers[pos].sup && comp(losers[pos].key, key)))
{
// The other one is smaller.
std::swap(losers[pos].sup, sup);
std::swap(losers[pos].source, source);
std::swap(losers[pos].key, key);
}
}
losers[0].sup = sup;
losers[0].source = source;
losers[0].key = key;
}
};
/**
* @brief Base class of Loser Tree implementation using pointers.
*/
template<typename T, typename Comparator>
class LoserTreePointerBase
{
protected:
/** @brief Internal representation of LoserTree elements. */
struct Loser
{
bool sup;
int source;
const T* keyp;
};
unsigned int ik, k, offset;
Loser* losers;
Comparator comp;
public:
LoserTreePointerBase(unsigned int _k, Comparator _comp = std::less<T>())
: comp(_comp)
{
ik = _k;
// Next greater power of 2.
k = 1 << (__log2(ik - 1) + 1);
offset = k;
losers = new Loser[k * 2];
for (unsigned int i = ik - 1; i < k; i++)
losers[i + k].sup = true;
}
~LoserTreePointerBase()
{ ::operator delete[](losers); }
int get_min_source()
{ return losers[0].source; }
void insert_start(const T& key, int source, bool sup)
{
unsigned int pos = k + source;
losers[pos].sup = sup;
losers[pos].source = source;
losers[pos].keyp = &key;
}
};
/**
* @brief Stable LoserTree implementation.
*
* The unstable variant is implemented using partial instantiation below.
*/
template<bool stable/* default == true */, typename T, typename Comparator>
class LoserTreePointer : public LoserTreePointerBase<T, Comparator>
{
typedef LoserTreePointerBase<T, Comparator> Base;
using Base::k;
using Base::losers;
public:
LoserTreePointer(unsigned int _k, Comparator _comp = std::less<T>())
: Base::LoserTreePointerBase(_k, _comp)
{}
unsigned int
init_winner(unsigned int root)
{
if (root >= k)
{
return root;
}
else
{
unsigned int left = init_winner (2 * root);
unsigned int right = init_winner (2 * root + 1);
if (losers[right].sup
|| (!losers[left].sup && !comp(*losers[right].keyp,
*losers[left].keyp)))
{
// Left one is less or equal.
losers[root] = losers[right];
return left;
}
else
{
// Right one is less.
losers[root] = losers[left];
return right;
}
}
}
void init()
{ losers[0] = losers[init_winner(1)]; }
void delete_min_insert(const T& key, bool sup)
{
#if _GLIBCXX_ASSERTIONS
// no dummy sequence can ever be at the top!
_GLIBCXX_PARALLEL_ASSERT(losers[0].source != -1);
#endif
const T* keyp = &key;
int source = losers[0].source;
for (unsigned int pos = (k + source) / 2; pos > 0; pos /= 2)
{
// The smaller one gets promoted, ties are broken by source.
if ((sup && (!losers[pos].sup || losers[pos].source < source)) ||
(!sup && !losers[pos].sup &&
((comp(*losers[pos].keyp, *keyp)) ||
(!comp(*keyp, *losers[pos].keyp)
&& losers[pos].source < source))))
{
// The other one is smaller.
std::swap(losers[pos].sup, sup);
std::swap(losers[pos].source, source);
std::swap(losers[pos].keyp, keyp);
}
}
losers[0].sup = sup;
losers[0].source = source;
losers[0].keyp = keyp;
}
};
/**
* @brief Unstable LoserTree implementation.
*
* The stable variant is above.
*/
template<typename T, typename Comparator>
class LoserTreePointer</* stable == */false, T, Comparator> :
public LoserTreePointerBase<T, Comparator>
{
typedef LoserTreePointerBase<T, Comparator> Base;
using Base::k;
using Base::losers;
public:
LoserTreePointer(unsigned int _k, Comparator _comp = std::less<T>())
: Base::LoserTreePointerBase(_k, _comp)
{}
unsigned int
init_winner(unsigned int root)
{
if (root >= k)
{
return root;
}
else
{
unsigned int left = init_winner (2 * root);
unsigned int right = init_winner (2 * root + 1);
if (losers[right].sup
|| (!losers[left].sup
&& !comp(*losers[right].keyp, *losers[left].keyp)))
{
// Left one is less or equal.
losers[root] = losers[right];
return left;
}
else
{
// Right one is less.
losers[root] = losers[left];
return right;
}
}
}
void init()
{ losers[0] = losers[init_winner(1)]; }
void delete_min_insert(const T& key, bool sup)
{
#if _GLIBCXX_ASSERTIONS
// no dummy sequence can ever be at the top!
_GLIBCXX_PARALLEL_ASSERT(losers[0].source != -1);
#endif
const T* keyp = &key;
int source = losers[0].source;
for (unsigned int pos = (k + source) / 2; pos > 0; pos /= 2)
{
// The smaller one gets promoted.
if (sup || (!losers[pos].sup && comp(*losers[pos].keyp, *keyp)))
{
// The other one is smaller.
std::swap(losers[pos].sup, sup);
std::swap(losers[pos].source, source);
std::swap(losers[pos].keyp, keyp);
}
}
losers[0].sup = sup;
losers[0].source = source;
losers[0].keyp = keyp;
}
};
/** @brief Base class for unguarded LoserTree implementation.
*
* The whole element is copied into the tree structure.
*
* No guarding is done, therefore not a single input sequence must
* run empty. Unused sequence heads are marked with a sentinel which
* is > all elements that are to be merged.
*
* This is a very fast variant.
*/
template<typename T, typename Comparator>
class LoserTreeUnguardedBase
{
protected:
struct Loser
{
int source;
T key;
};
unsigned int ik, k, offset;
Loser* losers;
Comparator comp;
public:
inline
LoserTreeUnguardedBase(unsigned int _k, const T _sentinel,
Comparator _comp = std::less<T>())
: comp(_comp)
{
ik = _k;
// Next greater power of 2.
k = 1 << (__log2(ik - 1) + 1);
offset = k;
// Avoid default-constructing losers[].key
losers = static_cast<Loser*>(::operator new(2 * k * sizeof(Loser)));
for (unsigned int i = k + ik - 1; i < (2 * k); ++i)
{
losers[i].key = _sentinel;
losers[i].source = -1;
}
}
inline ~LoserTreeUnguardedBase()
{ ::operator delete(losers); }
inline int
get_min_source()
{
#if _GLIBCXX_ASSERTIONS
// no dummy sequence can ever be at the top!
_GLIBCXX_PARALLEL_ASSERT(losers[0].source != -1);
#endif
return losers[0].source;
}
inline void
insert_start(const T& key, int source, bool)
{
unsigned int pos = k + source;
new(&(losers[pos].key)) T(key);
losers[pos].source = source;
}
};
/**
* @brief Stable implementation of unguarded LoserTree.
*
* Unstable variant is selected below with partial specialization.
*/
template<bool stable/* default == true */, typename T, typename Comparator>
class LoserTreeUnguarded : public LoserTreeUnguardedBase<T, Comparator>
{
typedef LoserTreeUnguardedBase<T, Comparator> Base;
using Base::k;
using Base::losers;
public:
LoserTreeUnguarded(unsigned int _k, const T _sentinel,
Comparator _comp = std::less<T>())
: Base::LoserTreeUnguardedBase(_k, _sentinel, _comp)
{}
unsigned int
init_winner(unsigned int root)
{
if (root >= k)
{
return root;
}
else
{
unsigned int left = init_winner (2 * root);
unsigned int right = init_winner (2 * root + 1);
if (!comp(losers[right].key, losers[left].key))
{
// Left one is less or equal.
losers[root] = losers[right];
return left;
}
else
{
// Right one is less.
losers[root] = losers[left];
return right;
}
}
}
inline void
init()
{
losers[0] = losers[init_winner(1)];
#if _GLIBCXX_ASSERTIONS
// no dummy sequence can ever be at the top at the beginning (0 sequences!)
_GLIBCXX_PARALLEL_ASSERT(losers[0].source != -1);
#endif
}
// Do not pass a const reference since key will be used as local variable.
inline void
delete_min_insert(T key, bool)
{
#if _GLIBCXX_ASSERTIONS
// no dummy sequence can ever be at the top!
_GLIBCXX_PARALLEL_ASSERT(losers[0].source != -1);
#endif
int source = losers[0].source;
for (unsigned int pos = (k + source) / 2; pos > 0; pos /= 2)
{
// The smaller one gets promoted, ties are broken by source.
if (comp(losers[pos].key, key)
|| (!comp(key, losers[pos].key) && losers[pos].source < source))
{
// The other one is smaller.
std::swap(losers[pos].source, source);
std::swap(losers[pos].key, key);
}
}
losers[0].source = source;
losers[0].key = key;
}
};
/**
* @brief Non-Stable implementation of unguarded LoserTree.
*
* Stable implementation is above.
*/
template<typename T, typename Comparator>
class LoserTreeUnguarded</* stable == */false, T, Comparator> :
public LoserTreeUnguardedBase<T, Comparator>
{
typedef LoserTreeUnguardedBase<T, Comparator> Base;
using Base::k;
using Base::losers;
public:
LoserTreeUnguarded(unsigned int _k, const T _sentinel,
Comparator _comp = std::less<T>())
: Base::LoserTreeUnguardedBase(_k, _sentinel, _comp)
{}
unsigned int
init_winner (unsigned int root)
{
if (root >= k)
{
return root;
}
else
{
unsigned int left = init_winner (2 * root);
unsigned int right = init_winner (2 * root + 1);
#if _GLIBCXX_ASSERTIONS
// If left one is sentinel then right one must be, too.
if (losers[left].source == -1)
_GLIBCXX_PARALLEL_ASSERT(losers[right].source == -1);
#endif
if (!comp(losers[right].key, losers[left].key))
{
// Left one is less or equal.
losers[root] = losers[right];
return left;
}
else
{
// Right one is less.
losers[root] = losers[left];
return right;
}
}
}
inline void
init()
{
losers[0] = losers[init_winner(1)];
#if _GLIBCXX_ASSERTIONS
// no dummy sequence can ever be at the top at the beginning (0 sequences!)
_GLIBCXX_PARALLEL_ASSERT(losers[0].source != -1);
#endif
}
// Do not pass a const reference since key will be used as local variable.
inline void
delete_min_insert(T key, bool)
{
#if _GLIBCXX_ASSERTIONS
// no dummy sequence can ever be at the top!
_GLIBCXX_PARALLEL_ASSERT(losers[0].source != -1);
#endif
int source = losers[0].source;
for (unsigned int pos = (k + source) / 2; pos > 0; pos /= 2)
{
// The smaller one gets promoted.
if (comp(losers[pos].key, key))
{
// The other one is smaller.
std::swap(losers[pos].source, source);
std::swap(losers[pos].key, key);
}
}
losers[0].source = source;
losers[0].key = key;
}
};
/** @brief Unguarded loser tree, keeping only pointers to the
* elements in the tree structure.
*
* No guarding is done, therefore not a single input sequence must
* run empty. This is a very fast variant.
*/
template<typename T, typename Comparator>
class LoserTreePointerUnguardedBase
{
protected:
struct Loser
{
int source;
const T* keyp;
};
unsigned int ik, k, offset;
Loser* losers;
Comparator comp;
public:
inline
LoserTreePointerUnguardedBase(unsigned int _k, const T& _sentinel,
Comparator _comp = std::less<T>())
: comp(_comp)
{
ik = _k;
// Next greater power of 2.
k = 1 << (__log2(ik - 1) + 1);
offset = k;
// Avoid default-constructing losers[].key
losers = new Loser[2 * k];
for (unsigned int i = k + ik - 1; i < (2 * k); ++i)
{
losers[i].keyp = &_sentinel;
losers[i].source = -1;
}
}
inline ~LoserTreePointerUnguardedBase()
{ delete[] losers; }
inline int
get_min_source()
{
#if _GLIBCXX_ASSERTIONS
// no dummy sequence can ever be at the top!
_GLIBCXX_PARALLEL_ASSERT(losers[0].source != -1);
#endif
return losers[0].source;
}
inline void
insert_start(const T& key, int source, bool)
{
unsigned int pos = k + source;
losers[pos].keyp = &key;
losers[pos].source = source;
}
};
/**
* @brief Stable unguarded LoserTree variant storing pointers.
*
* Unstable variant is implemented below using partial specialization.
*/
template<bool stable/* default == true */, typename T, typename Comparator>
class LoserTreePointerUnguarded :
public LoserTreePointerUnguardedBase<T, Comparator>
{
typedef LoserTreePointerUnguardedBase<T, Comparator> Base;
using Base::k;
using Base::losers;
public:
LoserTreePointerUnguarded(unsigned int _k, const T& _sentinel,
Comparator _comp = std::less<T>())
: Base::LoserTreePointerUnguardedBase(_k, _sentinel, _comp)
{}
unsigned int
init_winner(unsigned int root)
{
if (root >= k)
{
return root;
}
else
{
unsigned int left = init_winner (2 * root);
unsigned int right = init_winner (2 * root + 1);
if (!comp(*losers[right].keyp, *losers[left].keyp))
{
// Left one is less or equal.
losers[root] = losers[right];
return left;
}
else
{
// Right one is less.
losers[root] = losers[left];
return right;
}
}
}
inline void
init()
{
losers[0] = losers[init_winner(1)];
#if _GLIBCXX_ASSERTIONS
// no dummy sequence can ever be at the top at the beginning (0 sequences!)
_GLIBCXX_PARALLEL_ASSERT(losers[0].source != -1);
#endif
}
inline void
delete_min_insert(const T& key, bool sup)
{
#if _GLIBCXX_ASSERTIONS
// no dummy sequence can ever be at the top!
_GLIBCXX_PARALLEL_ASSERT(losers[0].source != -1);
#endif
const T* keyp = &key;
int source = losers[0].source;
for (unsigned int pos = (k + source) / 2; pos > 0; pos /= 2)
{
// The smaller one gets promoted, ties are broken by source.
if (comp(*losers[pos].keyp, *keyp)
|| (!comp(*keyp, *losers[pos].keyp) && losers[pos].source < source))
{
// The other one is smaller.
std::swap(losers[pos].source, source);
std::swap(losers[pos].keyp, keyp);
}
}
losers[0].source = source;
losers[0].keyp = keyp;
}
};
/**
* @brief Unstable unguarded LoserTree variant storing pointers.
*
* Stable variant is above.
*/
template<typename T, typename Comparator>
class LoserTreePointerUnguarded</* stable == */false, T, Comparator> :
public LoserTreePointerUnguardedBase<T, Comparator>
{
typedef LoserTreePointerUnguardedBase<T, Comparator> Base;
using Base::k;
using Base::losers;
public:
LoserTreePointerUnguarded(unsigned int _k, const T& _sentinel,
Comparator _comp = std::less<T>())
: Base::LoserTreePointerUnguardedBase(_k, _sentinel, _comp)
{}
unsigned int
init_winner(unsigned int root)
{
if (root >= k)
{
return root;
}
else
{
unsigned int left = init_winner (2 * root);
unsigned int right = init_winner (2 * root + 1);
#if _GLIBCXX_ASSERTIONS
// If left one is sentinel then right one must be, too.
if (losers[left].source == -1)
_GLIBCXX_PARALLEL_ASSERT(losers[right].source == -1);
#endif
if (!comp(*losers[right].keyp, *losers[left].keyp))
{
// Left one is less or equal.
losers[root] = losers[right];
return left;
}
else
{
// Right one is less.
losers[root] = losers[left];
return right;
}
}
}
inline void
init()
{
losers[0] = losers[init_winner(1)];
#if _GLIBCXX_ASSERTIONS
// no dummy sequence can ever be at the top at the beginning (0 sequences!)
_GLIBCXX_PARALLEL_ASSERT(losers[0].source != -1);
#endif
}
inline void
delete_min_insert(const T& key, bool sup)
{
#if _GLIBCXX_ASSERTIONS
// no dummy sequence can ever be at the top!
_GLIBCXX_PARALLEL_ASSERT(losers[0].source != -1);
#endif
const T* keyp = &key;
int source = losers[0].source;
for (unsigned int pos = (k + source) / 2; pos > 0; pos /= 2)
{
// The smaller one gets promoted.
if (comp(*(losers[pos].keyp), *keyp))
{
// The other one is smaller.
std::swap(losers[pos].source, source);
std::swap(losers[pos].keyp, keyp);
}
}
losers[0].source = source;
losers[0].keyp = keyp;
}
};
} // namespace __gnu_parallel
#endif /* _GLIBCXX_PARALLEL_LOSERTREE_H */