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dfs.hh
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4  * Christian Schulte <schulte@gecode.org>
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7  * Christian Schulte, 2009
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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  start();
108  while (true) {
109  while (cur) {
110  if (stop(opt))
111  return NULL;
112  node++;
113  switch (cur->status(*this)) {
114  case SS_FAILED:
115  fail++;
116  delete cur;
117  cur = NULL;
118  break;
119  case SS_SOLVED:
120  {
121  // Deletes all pending branchers
122  (void) cur->choice();
123  Space* s = cur;
124  cur = NULL;
125  return s;
126  }
127  case SS_BRANCH:
128  {
129  Space* c;
130  if ((d == 0) || (d >= opt.c_d)) {
131  c = cur->clone();
132  d = 1;
133  } else {
134  c = NULL;
135  d++;
136  }
137  const Choice* ch = path.push(*this,cur,c);
138  cur->commit(*ch,0);
139  break;
140  }
141  default:
142  GECODE_NEVER;
143  }
144  }
145  do {
146  if (!path.next())
147  return NULL;
148  cur = path.recompute(d,opt.a_d,*this);
149  } while (cur == NULL);
150  }
151  GECODE_NEVER;
152  return NULL;
153  }
154 
156  DFS::statistics(void) const {
157  return *this;
158  }
159 
160  forceinline
161  DFS::~DFS(void) {
162  delete cur;
163  path.reset();
164  }
165 
166 }}}
167 
168 #endif
169 
170 // 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:1266
~DFS(void)
Destructor.
Definition: dfs.hh:161
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:2777
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:1325
Statistics statistics(void) const
Return statistics.
Definition: dfs.hh:156
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:291
void commit(const Choice &c, unsigned int a, CommitStatistics &stat=unused_commit)
Commit choice c for alternative a.
Definition: core.hpp:2785
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
bool next(void)
Generate path for next node and return whether a next node exists.
Definition: path.hh:234
void reset(void)
Reset stack.
Definition: path.hh:285
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:129
SpaceStatus status(StatusStatistics &stat=unused_status)
Query space status.
Definition: core.cpp:251
Space * snapshot(Space *s, const Options &o, bool share=true)
Clone space s dependening on options o.
Definition: support.hh:73
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:1264
const Choice * choice(void)
Create new choice for current brancher.
Definition: core.cpp:365
#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
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:1265