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dfs.hh
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2 /*
3  * Main authors:
4  * Christian Schulte <schulte@gecode.org>
5  *
6  * Copyright:
7  * Christian Schulte, 2009
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10  * $Date: 2015-01-08 15:07:24 +0100 (Thu, 08 Jan 2015) $ by $Author: schulte $
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37 
38 #ifndef __GECODE_SEARCH_SEQUENTIAL_DFS_HH__
39 #define __GECODE_SEARCH_SEQUENTIAL_DFS_HH__
40 
41 #include <gecode/search.hh>
42 #include <gecode/search/support.hh>
43 #include <gecode/search/worker.hh>
45 
46 namespace Gecode { namespace Search { namespace Sequential {
47 
49  class DFS : public Worker {
50  private:
52  Options opt;
54  Path path;
56  Space* cur;
58  unsigned int d;
59  public:
61  DFS(Space* s, const Options& o);
63  Space* next(void);
65  Statistics statistics(void) const;
67  void reset(Space* s);
69  NoGoods& nogoods(void);
71  ~DFS(void);
72  };
73 
75  DFS::DFS(Space* s, const Options& o)
76  : opt(o), path(static_cast<int>(opt.nogoods_limit)), d(0) {
77  if ((s == NULL) || (s->status(*this) == SS_FAILED)) {
78  fail++;
79  cur = NULL;
80  if (!opt.clone)
81  delete s;
82  } else {
83  cur = snapshot(s,opt);
84  }
85  }
86 
87  forceinline void
89  delete cur;
90  path.reset();
91  d = 0;
92  if ((s == NULL) || (s->status(*this) == SS_FAILED)) {
93  cur = NULL;
94  } else {
95  cur = s;
96  }
97  Worker::reset();
98  }
99 
101  DFS::nogoods(void) {
102  return path;
103  }
104 
106  DFS::next(void) {
107  /*
108  * The engine maintains the following invariant:
109  * - If the current space (cur) is not NULL, the path always points
110  * to exactly that space.
111  * - If the current space (cur) is NULL, the path always points
112  * to the next space (if there is any).
113  *
114  * This invariant is needed so that no-goods can be extracted properly
115  * when the engine is stopped or has found a solution.
116  *
117  */
118  start();
119  while (true) {
120  if (stop(opt))
121  return NULL;
122  while (cur == NULL) {
123  if (path.empty())
124  return NULL;
125  cur = path.recompute(d,opt.a_d,*this);
126  if (cur != NULL)
127  break;
128  path.next();
129  }
130  node++;
131  switch (cur->status(*this)) {
132  case SS_FAILED:
133  fail++;
134  delete cur;
135  cur = NULL;
136  path.next();
137  break;
138  case SS_SOLVED:
139  {
140  // Deletes all pending branchers
141  (void) cur->choice();
142  Space* s = cur;
143  cur = NULL;
144  path.next();
145  return s;
146  }
147  case SS_BRANCH:
148  {
149  Space* c;
150  if ((d == 0) || (d >= opt.c_d)) {
151  c = cur->clone();
152  d = 1;
153  } else {
154  c = NULL;
155  d++;
156  }
157  const Choice* ch = path.push(*this,cur,c);
158  cur->commit(*ch,0);
159  break;
160  }
161  default:
162  GECODE_NEVER;
163  }
164  }
165  GECODE_NEVER;
166  return NULL;
167  }
168 
170  DFS::statistics(void) const {
171  return *this;
172  }
173 
174  forceinline
175  DFS::~DFS(void) {
176  delete cur;
177  path.reset();
178  }
179 
180 }}}
181 
182 #endif
183 
184 // STATISTICS: search-sequential
unsigned int a_d
Create a clone during recomputation if distance is greater than a_d (adaptive distance) ...
Definition: search.hh:213
Space must be branched (at least one brancher left)
Definition: core.hpp:1303
~DFS(void)
Destructor.
Definition: dfs.hh:175
Search engine statistics
Definition: search.hh:136
unsigned int c_d
Create a clone after every c_d commits (commit distance)
Definition: search.hh:211
Space * clone(bool share=true, CloneStatistics &stat=unused_clone) const
Clone space.
Definition: core.hpp:2854
Search engine options
Definition: search.hh:204
const Choice * push(Worker &stat, Space *s, Space *c)
Push space c (a clone of s or NULL)
Definition: path.hh:222
Space * next(void)
Search for next solution
Definition: dfs.hh:106
Depth-first path (stack of edges) supporting recomputation.
Definition: path.hh:61
unsigned long int fail
Number of failed nodes in search tree.
Definition: search.hh:139
void path(Home home, int offset, const IntVarArgs &x, IntVar s, IntVar e, IntConLevel icl)
Post propagator such that x forms a Hamiltonian path.
Definition: circuit.cpp:128
Computation spaces.
Definition: core.hpp:1362
Statistics statistics(void) const
Return statistics.
Definition: dfs.hh:170
Gecode::IntSet d(v, 7)
void start(void)
Reset stop information.
Definition: worker.hh:78
Gecode::FloatVal c(-8, 8)
Options opt
The options.
Definition: test.cpp:101
Space * recompute(unsigned int &d, unsigned int a_d, Worker &s)
Recompute space according to path.
Definition: path.hh:290
void commit(const Choice &c, unsigned int a, CommitStatistics &stat=unused_commit)
Commit choice c for alternative a.
Definition: core.hpp:2862
DFS(Space *s, const Options &o)
Initialize for space s with options o.
Definition: dfs.hh:75
bool clone
Whether engines create a clone when being initialized.
Definition: search.hh:207
void reset(void)
Reset stack.
Definition: path.hh:284
Search worker statistics
Definition: worker.hh:48
NoGoods & nogoods(void)
Return no-goods.
Definition: dfs.hh:101
Choice for performing commit
Definition: core.hpp:1036
No-goods recorded from restarts.
Definition: core.hpp:1240
#define forceinline
Definition: config.hpp:132
void next(void)
Generate path for next node.
Definition: path.hh:234
SpaceStatus status(StatusStatistics &stat=unused_status)
Query space status.
Definition: core.cpp:252
Space * snapshot(Space *s, const Options &o, bool share=true)
Clone space s dependening on options o.
Definition: support.hh:73
Gecode toplevel namespace
unsigned long int node
Number of nodes expanded.
Definition: search.hh:141
const unsigned int nogoods_limit
Depth limit for no-good generation during search.
Definition: search.hh:107
Space is failed
Definition: core.hpp:1301
const Choice * choice(void)
Create new choice for current brancher.
Definition: core.cpp:366
#define GECODE_NEVER
Assert that this command is never executed.
Definition: macros.hpp:60
bool stop(const Options &o)
Check whether engine must be stopped.
Definition: worker.hh:83
bool empty(void) const
Test whether path is empty.
Definition: path.hh:251
Depth-first search engine implementation.
Definition: dfs.hh:49
void reset(void)
Reset.
Definition: statistics.hpp:43
Space is solved (no brancher left)
Definition: core.hpp:1302