1/////////////////////////////////////////////////////////////////////////////
2//
3// (C) Copyright Ion Gaztanaga 2007-2014
4//
5// Distributed under the Boost Software License, Version 1.0.
6// (See accompanying file LICENSE_1_0.txt or copy at
7// http://www.boost.org/LICENSE_1_0.txt)
8//
9// See http://www.boost.org/libs/intrusive for documentation.
10//
11/////////////////////////////////////////////////////////////////////////////
12//
13// Scapegoat tree algorithms are taken from the paper titled:
14// "Scapegoat Trees" by Igal Galperin Ronald L. Rivest.
15//
16/////////////////////////////////////////////////////////////////////////////
17#ifndef BOOST_INTRUSIVE_SGTREE_ALGORITHMS_HPP
18#define BOOST_INTRUSIVE_SGTREE_ALGORITHMS_HPP
19
20#include <boost/intrusive/detail/config_begin.hpp>
21#include <boost/intrusive/intrusive_fwd.hpp>
22
23#include <cstddef>
24#include <boost/intrusive/detail/algo_type.hpp>
25#include <boost/intrusive/bstree_algorithms.hpp>
26
27#if defined(BOOST_HAS_PRAGMA_ONCE)
28# pragma once
29#endif
30
31namespace boost {
32namespace intrusive {
33
34//! sgtree_algorithms is configured with a NodeTraits class, which encapsulates the
35//! information about the node to be manipulated. NodeTraits must support the
36//! following interface:
37//!
38//! <b>Typedefs</b>:
39//!
40//! <tt>node</tt>: The type of the node that forms the binary search tree
41//!
42//! <tt>node_ptr</tt>: A pointer to a node
43//!
44//! <tt>const_node_ptr</tt>: A pointer to a const node
45//!
46//! <b>Static functions</b>:
47//!
48//! <tt>static node_ptr get_parent(const_node_ptr n);</tt>
49//!
50//! <tt>static void set_parent(node_ptr n, node_ptr parent);</tt>
51//!
52//! <tt>static node_ptr get_left(const_node_ptr n);</tt>
53//!
54//! <tt>static void set_left(node_ptr n, node_ptr left);</tt>
55//!
56//! <tt>static node_ptr get_right(const_node_ptr n);</tt>
57//!
58//! <tt>static void set_right(node_ptr n, node_ptr right);</tt>
59template<class NodeTraits>
60class sgtree_algorithms
61 #ifndef BOOST_INTRUSIVE_DOXYGEN_INVOKED
62 : public bstree_algorithms<NodeTraits>
63 #endif
64{
65 public:
66 typedef typename NodeTraits::node node;
67 typedef NodeTraits node_traits;
68 typedef typename NodeTraits::node_ptr node_ptr;
69 typedef typename NodeTraits::const_node_ptr const_node_ptr;
70
71 /// @cond
72 private:
73
74 typedef bstree_algorithms<NodeTraits> bstree_algo;
75
76 /// @endcond
77
78 public:
79 //! This type is the information that will be
80 //! filled by insert_unique_check
81 struct insert_commit_data
82 : bstree_algo::insert_commit_data
83 {
84 std::size_t depth;
85 };
86
87 #ifdef BOOST_INTRUSIVE_DOXYGEN_INVOKED
88 //! @copydoc ::boost::intrusive::bstree_algorithms::get_header(const const_node_ptr&)
89 static node_ptr get_header(const const_node_ptr & n);
90
91 //! @copydoc ::boost::intrusive::bstree_algorithms::begin_node
92 static node_ptr begin_node(const const_node_ptr & header);
93
94 //! @copydoc ::boost::intrusive::bstree_algorithms::end_node
95 static node_ptr end_node(const const_node_ptr & header);
96
97 //! @copydoc ::boost::intrusive::bstree_algorithms::swap_tree
98 static void swap_tree(const node_ptr & header1, const node_ptr & header2);
99
100 //! @copydoc ::boost::intrusive::bstree_algorithms::swap_nodes(const node_ptr&,const node_ptr&)
101 static void swap_nodes(const node_ptr & node1, const node_ptr & node2);
102
103 //! @copydoc ::boost::intrusive::bstree_algorithms::swap_nodes(const node_ptr&,const node_ptr&,const node_ptr&,const node_ptr&)
104 static void swap_nodes(const node_ptr & node1, const node_ptr & header1, const node_ptr & node2, const node_ptr & header2);
105
106 //! @copydoc ::boost::intrusive::bstree_algorithms::replace_node(const node_ptr&,const node_ptr&)
107 static void replace_node(const node_ptr & node_to_be_replaced, const node_ptr & new_node);
108
109 //! @copydoc ::boost::intrusive::bstree_algorithms::replace_node(const node_ptr&,const node_ptr&,const node_ptr&)
110 static void replace_node(const node_ptr & node_to_be_replaced, const node_ptr & header, const node_ptr & new_node);
111
112 //Unlink is not possible since tree metadata is needed to update the tree
113 //!static void unlink(const node_ptr & node);
114
115 //! @copydoc ::boost::intrusive::bstree_algorithms::unlink_leftmost_without_rebalance
116 static node_ptr unlink_leftmost_without_rebalance(const node_ptr & header);
117
118 //! @copydoc ::boost::intrusive::bstree_algorithms::unique(const const_node_ptr&)
119 static bool unique(const const_node_ptr & node);
120
121 //! @copydoc ::boost::intrusive::bstree_algorithms::size(const const_node_ptr&)
122 static std::size_t size(const const_node_ptr & header);
123
124 //! @copydoc ::boost::intrusive::bstree_algorithms::next_node(const node_ptr&)
125 static node_ptr next_node(const node_ptr & node);
126
127 //! @copydoc ::boost::intrusive::bstree_algorithms::prev_node(const node_ptr&)
128 static node_ptr prev_node(const node_ptr & node);
129
130 //! @copydoc ::boost::intrusive::bstree_algorithms::init(const node_ptr&)
131 static void init(const node_ptr & node);
132
133 //! @copydoc ::boost::intrusive::bstree_algorithms::init_header(const node_ptr&)
134 static void init_header(const node_ptr & header);
135 #endif //#ifdef BOOST_INTRUSIVE_DOXYGEN_INVOKED
136
137 //! @copydoc ::boost::intrusive::bstree_algorithms::erase(const node_ptr&,const node_ptr&)
138 template<class AlphaByMaxSize>
139 static node_ptr erase(const node_ptr & header, const node_ptr & z, std::size_t tree_size, std::size_t &max_tree_size, AlphaByMaxSize alpha_by_maxsize)
140 {
141 //typename bstree_algo::data_for_rebalance info;
142 bstree_algo::erase(header, z);
143 --tree_size;
144 if (tree_size > 0 &&
145 tree_size < alpha_by_maxsize(max_tree_size)){
146 bstree_algo::rebalance(header);
147 max_tree_size = tree_size;
148 }
149 return z;
150 }
151
152 #ifdef BOOST_INTRUSIVE_DOXYGEN_INVOKED
153 //! @copydoc ::boost::intrusive::bstree_algorithms::clone(const const_node_ptr&,const node_ptr&,Cloner,Disposer)
154 template <class Cloner, class Disposer>
155 static void clone
156 (const const_node_ptr & source_header, const node_ptr & target_header, Cloner cloner, Disposer disposer);
157
158 //! @copydoc ::boost::intrusive::bstree_algorithms::clear_and_dispose(const node_ptr&,Disposer)
159 template<class Disposer>
160 static void clear_and_dispose(const node_ptr & header, Disposer disposer);
161
162 //! @copydoc ::boost::intrusive::bstree_algorithms::lower_bound(const const_node_ptr&,const KeyType&,KeyNodePtrCompare)
163 template<class KeyType, class KeyNodePtrCompare>
164 static node_ptr lower_bound
165 (const const_node_ptr & header, const KeyType &key, KeyNodePtrCompare comp);
166
167 //! @copydoc ::boost::intrusive::bstree_algorithms::upper_bound(const const_node_ptr&,const KeyType&,KeyNodePtrCompare)
168 template<class KeyType, class KeyNodePtrCompare>
169 static node_ptr upper_bound
170 (const const_node_ptr & header, const KeyType &key, KeyNodePtrCompare comp);
171
172 //! @copydoc ::boost::intrusive::bstree_algorithms::find(const const_node_ptr&, const KeyType&,KeyNodePtrCompare)
173 template<class KeyType, class KeyNodePtrCompare>
174 static node_ptr find
175 (const const_node_ptr & header, const KeyType &key, KeyNodePtrCompare comp);
176
177 //! @copydoc ::boost::intrusive::bstree_algorithms::equal_range(const const_node_ptr&,const KeyType&,KeyNodePtrCompare)
178 template<class KeyType, class KeyNodePtrCompare>
179 static std::pair<node_ptr, node_ptr> equal_range
180 (const const_node_ptr & header, const KeyType &key, KeyNodePtrCompare comp);
181
182 //! @copydoc ::boost::intrusive::bstree_algorithms::bounded_range(const const_node_ptr&,const KeyType&,const KeyType&,KeyNodePtrCompare,bool,bool)
183 template<class KeyType, class KeyNodePtrCompare>
184 static std::pair<node_ptr, node_ptr> bounded_range
185 (const const_node_ptr & header, const KeyType &lower_key, const KeyType &upper_key, KeyNodePtrCompare comp
186 , bool left_closed, bool right_closed);
187
188 //! @copydoc ::boost::intrusive::bstree_algorithms::count(const const_node_ptr&,const KeyType&,KeyNodePtrCompare)
189 template<class KeyType, class KeyNodePtrCompare>
190 static std::size_t count(const const_node_ptr & header, const KeyType &key, KeyNodePtrCompare comp);
191
192 #endif //#ifdef BOOST_INTRUSIVE_DOXYGEN_INVOKED
193
194 //! @copydoc ::boost::intrusive::bstree_algorithms::insert_equal_upper_bound(const node_ptr&,const node_ptr&,NodePtrCompare)
195 template<class NodePtrCompare, class H_Alpha>
196 static node_ptr insert_equal_upper_bound
197 (const node_ptr & h, const node_ptr & new_node, NodePtrCompare comp
198 ,std::size_t tree_size, H_Alpha h_alpha, std::size_t &max_tree_size)
199 {
200 std::size_t depth;
201 bstree_algo::insert_equal_upper_bound(h, new_node, comp, &depth);
202 rebalance_after_insertion(new_node, depth, tree_size+1, h_alpha, max_tree_size);
203 return new_node;
204 }
205
206 //! @copydoc ::boost::intrusive::bstree_algorithms::insert_equal_lower_bound(const node_ptr&,const node_ptr&,NodePtrCompare)
207 template<class NodePtrCompare, class H_Alpha>
208 static node_ptr insert_equal_lower_bound
209 (const node_ptr & h, const node_ptr & new_node, NodePtrCompare comp
210 ,std::size_t tree_size, H_Alpha h_alpha, std::size_t &max_tree_size)
211 {
212 std::size_t depth;
213 bstree_algo::insert_equal_lower_bound(h, new_node, comp, &depth);
214 rebalance_after_insertion(new_node, depth, tree_size+1, h_alpha, max_tree_size);
215 return new_node;
216 }
217
218 //! @copydoc ::boost::intrusive::bstree_algorithms::insert_equal(const node_ptr&,const node_ptr&,const node_ptr&,NodePtrCompare)
219 template<class NodePtrCompare, class H_Alpha>
220 static node_ptr insert_equal
221 (const node_ptr & header, const node_ptr & hint, const node_ptr & new_node, NodePtrCompare comp
222 ,std::size_t tree_size, H_Alpha h_alpha, std::size_t &max_tree_size)
223 {
224 std::size_t depth;
225 bstree_algo::insert_equal(header, hint, new_node, comp, &depth);
226 rebalance_after_insertion(new_node, depth, tree_size+1, h_alpha, max_tree_size);
227 return new_node;
228 }
229
230 //! @copydoc ::boost::intrusive::bstree_algorithms::insert_before(const node_ptr&,const node_ptr&,const node_ptr&)
231 template<class H_Alpha>
232 static node_ptr insert_before
233 (const node_ptr & header, const node_ptr & pos, const node_ptr & new_node
234 ,std::size_t tree_size, H_Alpha h_alpha, std::size_t &max_tree_size)
235 {
236 std::size_t depth;
237 bstree_algo::insert_before(header, pos, new_node, &depth);
238 rebalance_after_insertion(new_node, depth, tree_size+1, h_alpha, max_tree_size);
239 return new_node;
240 }
241
242 //! @copydoc ::boost::intrusive::bstree_algorithms::push_back(const node_ptr&,const node_ptr&)
243 template<class H_Alpha>
244 static void push_back(const node_ptr & header, const node_ptr & new_node
245 ,std::size_t tree_size, H_Alpha h_alpha, std::size_t &max_tree_size)
246 {
247 std::size_t depth;
248 bstree_algo::push_back(header, new_node, &depth);
249 rebalance_after_insertion(new_node, depth, tree_size+1, h_alpha, max_tree_size);
250 }
251
252 //! @copydoc ::boost::intrusive::bstree_algorithms::push_front(const node_ptr&,const node_ptr&)
253 template<class H_Alpha>
254 static void push_front(const node_ptr & header, const node_ptr & new_node
255 ,std::size_t tree_size, H_Alpha h_alpha, std::size_t &max_tree_size)
256 {
257 std::size_t depth;
258 bstree_algo::push_front(header, new_node, &depth);
259 rebalance_after_insertion(new_node, depth, tree_size+1, h_alpha, max_tree_size);
260 }
261
262 //! @copydoc ::boost::intrusive::bstree_algorithms::insert_unique_check(const const_node_ptr&,const KeyType&,KeyNodePtrCompare,insert_commit_data&)
263 template<class KeyType, class KeyNodePtrCompare>
264 static std::pair<node_ptr, bool> insert_unique_check
265 (const const_node_ptr & header, const KeyType &key
266 ,KeyNodePtrCompare comp, insert_commit_data &commit_data)
267 {
268 std::size_t depth;
269 std::pair<node_ptr, bool> ret =
270 bstree_algo::insert_unique_check(header, key, comp, commit_data, &depth);
271 commit_data.depth = depth;
272 return ret;
273 }
274
275 //! @copydoc ::boost::intrusive::bstree_algorithms::insert_unique_check(const const_node_ptr&,const node_ptr&,const KeyType&,KeyNodePtrCompare,insert_commit_data&)
276 template<class KeyType, class KeyNodePtrCompare>
277 static std::pair<node_ptr, bool> insert_unique_check
278 (const const_node_ptr & header, const node_ptr &hint, const KeyType &key
279 ,KeyNodePtrCompare comp, insert_commit_data &commit_data)
280 {
281 std::size_t depth;
282 std::pair<node_ptr, bool> ret =
283 bstree_algo::insert_unique_check
284 (header, hint, key, comp, commit_data, &depth);
285 commit_data.depth = depth;
286 return ret;
287 }
288
289 //! @copydoc ::boost::intrusive::bstree_algorithms::insert_unique_commit(const node_ptr&,const node_ptr&,const insert_commit_data&)
290 template<class H_Alpha>
291 static void insert_unique_commit
292 (const node_ptr & header, const node_ptr & new_value, const insert_commit_data &commit_data
293 ,std::size_t tree_size, H_Alpha h_alpha, std::size_t &max_tree_size)
294 {
295 bstree_algo::insert_unique_commit(header, new_value, commit_data);
296 rebalance_after_insertion(new_value, commit_data.depth, tree_size+1, h_alpha, max_tree_size);
297 }
298
299 #ifdef BOOST_INTRUSIVE_DOXYGEN_INVOKED
300 //! @copydoc ::boost::intrusive::bstree_algorithms::is_header
301 static bool is_header(const const_node_ptr & p);
302
303 //! @copydoc ::boost::intrusive::bstree_algorithms::is_header
304 static void rebalance(const node_ptr & header);
305
306 //! @copydoc ::boost::intrusive::bstree_algorithms::rebalance_subtree
307 static node_ptr rebalance_subtree(const node_ptr & old_root)
308 #endif //#ifdef BOOST_INTRUSIVE_DOXYGEN_INVOKED
309
310 /// @cond
311 private:
312
313 template<class H_Alpha>
314 static void rebalance_after_insertion
315 (const node_ptr &x, std::size_t depth
316 , std::size_t tree_size, H_Alpha h_alpha, std::size_t &max_tree_size)
317 {
318 if(tree_size > max_tree_size)
319 max_tree_size = tree_size;
320
321 if(tree_size > 2 && //Nothing to do with only the root
322 //Check if the root node is unbalanced
323 //Scapegoat paper depth counts root depth as zero and "depth" counts root as 1,
324 //but since "depth" is the depth of the ancestor of x, i == depth
325 depth > h_alpha(tree_size)){
326
327 //Find the first non height-balanced node
328 //as described in the section 4.2 of the paper.
329 //This method is the alternative method described
330 //in the paper. Authors claim that this method
331 //may tend to yield more balanced trees on the average
332 //than the weight balanced method.
333 node_ptr s = x;
334 std::size_t size = 1;
335 for(std::size_t ancestor = 1; ancestor != depth; ++ancestor){
336 const node_ptr s_parent = NodeTraits::get_parent(s);
337 const node_ptr s_parent_left = NodeTraits::get_left(s_parent);
338 //Obtain parent's size (previous size + parent + sibling tree)
339 const node_ptr s_sibling = s_parent_left == s ? NodeTraits::get_right(s_parent) : s_parent_left;
340 size += 1 + bstree_algo::subtree_size(s_sibling);
341 s = s_parent;
342 if(ancestor > h_alpha(size)){ //is 's' scapegoat?
343 bstree_algo::rebalance_subtree(s);
344 return;
345 }
346 }
347 //The whole tree must be rebuilt
348 max_tree_size = tree_size;
349 bstree_algo::rebalance_subtree(NodeTraits::get_parent(s));
350 }
351 }
352 /// @endcond
353};
354
355/// @cond
356
357template<class NodeTraits>
358struct get_algo<SgTreeAlgorithms, NodeTraits>
359{
360 typedef sgtree_algorithms<NodeTraits> type;
361};
362
363template <class ValueTraits, class NodePtrCompare, class ExtraChecker>
364struct get_node_checker<SgTreeAlgorithms, ValueTraits, NodePtrCompare, ExtraChecker>
365{
366 typedef detail::bstree_node_checker<ValueTraits, NodePtrCompare, ExtraChecker> type;
367};
368
369/// @endcond
370
371} //namespace intrusive
372} //namespace boost
373
374#include <boost/intrusive/detail/config_end.hpp>
375
376#endif //BOOST_INTRUSIVE_SGTREE_ALGORITHMS_HPP
377

source code of boost/boost/intrusive/sgtree_algorithms.hpp