this repo has no description
dekker.one
1/* -*- mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*- */
2/*
3 * Main authors:
4 * Guido Tack <tack@gecode.org>
5 *
6 * Copyright:
7 * Guido Tack, 2006
8 *
9 * This file is part of Gecode, the generic constraint
10 * development environment:
11 * http://www.gecode.org
12 *
13 * Permission is hereby granted, free of charge, to any person obtaining
14 * a copy of this software and associated documentation files (the
15 * "Software"), to deal in the Software without restriction, including
16 * without limitation the rights to use, copy, modify, merge, publish,
17 * distribute, sublicense, and/or sell copies of the Software, and to
18 * permit persons to whom the Software is furnished to do so, subject to
19 * the following conditions:
20 *
21 * The above copyright notice and this permission notice shall be
22 * included in all copies or substantial portions of the Software.
23 *
24 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
25 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
26 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
27 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
28 * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
29 * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
30 * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
31 *
32 */
33
34#ifndef GECODE_GIST_SPACENODE_HH
35#define GECODE_GIST_SPACENODE_HH
36
37#include <gecode/gist/node.hh>
38#include <gecode/kernel.hh>
39
40namespace Gecode { namespace Gist {
41
42 /** \brief Status of nodes in the search tree
43 */
44 enum NodeStatus {
45 SOLVED, ///< Node representing a solution
46 FAILED, ///< Node representing failure
47 BRANCH, ///< Node representing a branch
48 UNDETERMINED, ///< Node that has not been explored yet
49 STOP, ///< Node representing stop point
50 UNSTOP, ///< Node representing ignored stop point
51 };
52
53 static const unsigned int FIRSTBIT = 24; //< First free bit in status word
54 static const unsigned int STATUSMASK = 7<<20; //< Mask for accessing status
55 static const unsigned int MAXDISTANCE = (1<<20)-1; //< Maximum representable distance
56 static const unsigned int DISTANCEMASK = (1<<20)-1; //< Mask for accessing distance
57
58 /// %Statistics about the search tree
59 class Statistics : public StatusStatistics {
60 public:
61 /// Number of solutions
62 int solutions;
63 /// Number of failures
64 int failures;
65 /// Number of choice nodes
66 int choices;
67 /// Number of open, undetermined nodes
68 int undetermined;
69 /// Maximum depth of the tree
70 int maxDepth;
71
72 /// Constructor
73 Statistics(void)
74 : solutions(0), failures(0), choices(0), undetermined(1), maxDepth(0) {}
75 };
76
77 class SpaceNode;
78
79 /// \brief Static reference to the currently best space
80 class BestNode {
81 public:
82 /// The currently best node found, or nullptr
83 SpaceNode* s;
84 /// Constructor
85 BestNode(SpaceNode* s0);
86 };
87
88 /// \brief A node of a search tree of %Gecode spaces
89 class SpaceNode : public Node {
90 protected:
91 /** \brief A copy used for recomputation, or nullptr
92 *
93 * If the copy is marked, it is a working copy, i.e.,
94 * it does not have to be kept for recomputation.
95 */
96 Space* copy;
97 protected:
98 const Choice* choice;
99
100 /** \brief Status of the node
101 *
102 * If the node has a working copy, the first 20 bits encode the distance
103 * to the closest copy. The next 5 bits encode the NodeStatus, and the
104 * remaining bits are used by the VisualNode class for further flags.
105 */
106 unsigned int nstatus;
107
108 /// Set distance from copy
109 void setDistance(unsigned int d);
110
111 /// Return distance from copy
112 unsigned int getDistance(void) const;
113
114 /// Set status flag
115 void setFlag(int flag, bool value);
116
117 /// Return status flag
118 bool getFlag(int flag) const;
119
120 /// Flags for SpaceNodes
121 enum SpaceNodeFlags {
122 HASOPENCHILDREN = FIRSTBIT,
123 HASFAILEDCHILDREN,
124 HASSOLVEDCHILDREN
125 };
126 /// Last bit used for SpaceNode flags
127 static const int LASTBIT = HASSOLVEDCHILDREN;
128
129 private:
130 /// Set whether the node has children that are not fully explored
131 void setHasOpenChildren(bool b);
132 /// Set whether the subtree of this node is known to contain failure
133 void setHasFailedChildren(bool b);
134 /// Set whether the subtree of this node is known to contain solutions
135 void setHasSolvedChildren(bool b);
136
137 /// Recompute workingSpace from a copy higher up, return distance to copy
138 int recompute(NodeAllocator& na,
139 BestNode* curBest, int c_d, int a_d);
140
141 /// Book-keeping of open children
142 void closeChild(const NodeAllocator& na,
143 bool hadFailures, bool hadSolutions);
144 protected:
145 /// Set status to \a s
146 void setStatus(NodeStatus s);
147 /// Acquire working space, either from parent or by recomputation
148 void acquireSpace(NodeAllocator& na,
149 BestNode* curBest, int c_d, int a_d);
150 public:
151 /// Construct node with parent \a p
152 SpaceNode(int p);
153 /// Construct root node from Space \a root and branch-and-bound object \a better
154 SpaceNode(Space* root);
155
156 /// Return working space. Receiver must delete the space.
157 Space* getSpace(NodeAllocator& na,
158 BestNode* curBest, int c_d, int a_d);
159
160 /// Return working space (if present).
161 const Space* getWorkingSpace(void) const;
162
163 /// Clear working space and copy (if present and this is not the root).
164 void purge(const NodeAllocator& na);
165
166 /// Free allocated memory
167 void dispose(void);
168
169 /// Return whether this node is the currently best solution
170 bool isCurrentBest(BestNode* curBest);
171
172 /** \brief Compute and return the number of children
173 *
174 * On a node whose status is already determined, this function
175 * just returns the number of children. On an undetermined node,
176 * it first acquires a Space (possibly through recomputation), and
177 * then asks for its status. If the space is solved or failed, the
178 * node's status will be set accordingly, and 0 will be returned.
179 * Otherwise, the status is SS_BRANCH, and as many new children will
180 * be created as the branch has alternatives, and the number returned.
181 */
182 int getNumberOfChildNodes(NodeAllocator& na,
183 BestNode* curBest,
184 Statistics& stats,
185 int c_d, int a_d);
186
187 /// Return current status of the node
188 NodeStatus getStatus(void) const;
189
190 /// Return whether this node still has open children
191 bool isOpen(void);
192 /// Return whether the subtree of this node has any failed children
193 bool hasFailedChildren(void);
194 /// Return whether the subtree of this node has any solved children
195 bool hasSolvedChildren(void);
196 /// Return whether the subtree of this node has any open children
197 bool hasOpenChildren(void);
198 /// Return number of open children
199 int getNoOfOpenChildren(const NodeAllocator& na);
200 /// Set number of open children to \a n
201 void setNoOfOpenChildren(int n);
202 /// Return whether the node has a copy
203 bool hasCopy(void);
204 /// Return whether the node has a working space
205 bool hasWorkingSpace(void);
206
207 /// Return alternative number of this node
208 int getAlternative(const NodeAllocator& na) const;
209 /// Return choice of this node
210 const Choice* getChoice(void);
211 };
212
213}}
214
215#endif
216
217// STATISTICS: gist-any