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bab.hh
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1 /* -*- mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*- */
2 /*
3  * Main authors:
4  * Christian Schulte <schulte@gecode.org>
5  *
6  * Copyright:
7  * Christian Schulte, 2009
8  *
9  * Last modified:
10  * $Date: 2013-07-11 12:30:18 +0200 (Thu, 11 Jul 2013) $ by $Author: schulte $
11  * $Revision: 13840 $
12  *
13  * This file is part of Gecode, the generic constraint
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37 
38 #ifndef __GECODE_SEARCH_PARALLEL_BAB_HH__
39 #define __GECODE_SEARCH_PARALLEL_BAB_HH__
40 
42 
43 namespace Gecode { namespace Search { namespace Parallel {
44 
46  class BAB : public Engine {
47  protected:
49  class Worker : public Engine::Worker {
50  protected:
52  int mark;
55  public:
57  Worker(Space* s, BAB& e);
59  BAB& engine(void) const;
61  virtual void run(void);
63  void better(Space* b);
65  void find(void);
67  void reset(Space* s, int ngdl);
69  virtual ~Worker(void);
70  };
75  public:
77  Worker* worker(unsigned int i) const;
78 
80 
81  void solution(Space* s);
84 
86 
87  BAB(Space* s, const Options& o);
90  virtual Statistics statistics(void) const;
92  virtual void reset(Space* s);
94  virtual NoGoods& nogoods(void);
96  virtual ~BAB(void);
98  };
99 
100 
101 
102  /*
103  * Engine: basic access routines
104  */
106  BAB::Worker::engine(void) const {
107  return static_cast<BAB&>(_engine);
108  }
110  BAB::worker(unsigned int i) const {
111  return _worker[i];
112  }
113 
114  forceinline void
115  BAB::Worker::reset(Space* s, int ngdl) {
116  delete cur;
117  delete best;
118  best = NULL;
119  path.reset((s == NULL) ? 0 : ngdl);
120  d = mark = 0;
121  idle = false;
122  if ((s == NULL) || (s->status(*this) == SS_FAILED)) {
123  delete s;
124  cur = NULL;
125  } else {
126  cur = s;
127  }
129  }
130 
131 
132  /*
133  * Engine: initialization
134  */
137  : Engine::Worker(s,e), mark(0), best(NULL) {}
138 
140  BAB::BAB(Space* s, const Options& o)
141  : Engine(o), best(NULL) {
142  // Create workers
143  _worker = static_cast<Worker**>
144  (heap.ralloc(workers() * sizeof(Worker*)));
145  // The first worker gets the entire search tree
146  _worker[0] = new Worker(s,*this);
147  // All other workers start with no work
148  for (unsigned int i=1; i<workers(); i++)
149  _worker[i] = new Worker(NULL,*this);
150  // Block all workers
151  block();
152  // Create and start threads
153  for (unsigned int i=0; i<workers(); i++)
155  }
156 
157 
158  /*
159  * Engine: search control
160  */
161  forceinline void
163  m.acquire();
164  delete best;
165  best = b->clone(false);
166  mark = path.entries();
167  if (cur != NULL)
168  cur->constrain(*best);
169  m.release();
170  }
171  forceinline void
173  m_search.acquire();
174  if (best != NULL) {
175  s->constrain(*best);
176  if (s->status() == SS_FAILED) {
177  delete s;
178  m_search.release();
179  return;
180  } else {
181  delete best;
182  best = s->clone();
183  }
184  } else {
185  best = s->clone();
186  }
187  // Announce better solutions
188  for (unsigned int i=0; i<workers(); i++)
189  worker(i)->better(best);
190  bool bs = signal();
191  solutions.push(s);
192  if (bs)
193  e_search.signal();
194  m_search.release();
195  }
196 
197 
198  /*
199  * Worker: finding and stealing working
200  */
201  forceinline void
203  // Try to find new work (even if there is none)
204  for (unsigned int i=0; i<engine().workers(); i++) {
205  unsigned long int r_d = 0ul;
206  if (Space* s = engine().worker(i)->steal(r_d)) {
207  // Reset this guy
208  m.acquire();
209  idle = false;
210  // Not idle but also does not have the root of the tree
211  path.ngdl(0);
212  d = 0;
213  cur = s;
214  mark = 0;
215  if (best != NULL)
216  cur->constrain(*best);
218  m.release();
219  return;
220  }
221  }
222  }
223 
224 }}}
225 
226 #endif
227 
228 // STATISTICS: search-parallel
Worker(void)
Initialize.
Definition: worker.hh:74
Worker * worker(unsigned int i) const
Provide access to worker i.
Definition: bab.hh:110
Path path
Current path ins search tree.
Definition: engine.hh:59
Search engine statistics
Definition: search.hh:136
virtual ~BAB(void)
Destructor.
Definition: bab.cpp:238
virtual Statistics statistics(void) const
Return statistics.
Definition: bab.cpp:50
Space * clone(bool share=true, CloneStatistics &stat=unused_clone) const
Clone space.
Definition: core.hpp:2854
void idle(void)
Report that worker is idle.
Definition: engine.hh:293
Search engine options
Definition: search.hh:204
static void run(Runnable *r)
Construct a new thread and run r.
Definition: thread.hpp:109
virtual void reset(Space *s)
Reset engine to restart at space s.
Definition: bab.cpp:185
void acquire(void)
Acquire the mutex and possibly block.
Definition: none.hpp:46
void * ralloc(size_t s)
Allocate s bytes from heap.
Definition: heap.hpp:341
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
void * mark(void *p)
Return marked pointer for p.
void block(void)
Block all workers.
Definition: engine.hh:222
void signal(void)
Signal the event.
Definition: none.hpp:63
Computation spaces.
Definition: core.hpp:1362
Parallel branch-and-bound search worker
Definition: bab.hh:49
void better(Space *b)
Accept better solution b.
Definition: bab.hh:162
Heap heap
The single global heap.
Definition: heap.cpp:49
Gecode::IntSet d(v, 7)
void release(void)
Release the mutex.
Definition: none.hpp:52
BAB(Space *s, const Options &o)
Initialize for space s with options o.
Definition: bab.hh:140
Gecode::IntArgs i(4, 1, 2, 3, 4)
virtual void constrain(const Space &best)
Constrain function for best solution search.
Definition: core.cpp:645
int entries(void) const
Return number of entries on stack.
Definition: path.hh:292
Space * cur
Current space being explored.
Definition: engine.hh:61
unsigned int workers(void) const
Return number of workers.
Definition: engine.hh:209
virtual ~Worker(void)
Destructor.
Definition: bab.cpp:234
void find(void)
Try to find some work.
Definition: bab.hh:202
virtual NoGoods & nogoods(void)
Return no-goods.
Definition: bab.cpp:213
Support::Event e_search
Event for search (solution found, no more solutions, search stopped)
Definition: engine.hh:167
Space * best
Best solution found so far.
Definition: bab.hh:54
Parallel depth-first search engine
Definition: engine.hh:49
int mark
Number of entries not yet constrained to be better.
Definition: bab.hh:52
BAB & engine(void) const
Provide access to engine.
Definition: bab.hh:106
No-goods recorded from restarts.
Definition: core.hpp:1240
Parallel branch-and-bound engine
Definition: bab.hh:46
#define forceinline
Definition: config.hpp:132
void solution(Space *s)
Report solution s.
Definition: bab.hh:172
Parallel depth-first search worker
Definition: engine.hh:52
SpaceStatus status(StatusStatistics &stat=unused_status)
Query space status.
Definition: core.cpp:252
Support::DynamicQueue< Space *, Heap > solutions
Queue of solutions.
Definition: engine.hh:169
Engine & _engine
Reference to engine.
Definition: engine.hh:55
struct Gecode::@518::NNF::@57::@58 b
For binary nodes (and, or, eqv)
Gecode toplevel namespace
Worker ** _worker
Array of worker references.
Definition: bab.hh:72
Space * best
Best solution so far.
Definition: bab.hh:74
virtual void run(void)
Start execution of worker.
Definition: bab.cpp:61
Space is failed
Definition: core.hpp:1301
Support::Mutex m
Mutex for access to worker.
Definition: engine.hh:57
bool signal(void) const
Whether search state changed such that signal is needed.
Definition: engine.hh:289
void reset(void)
Reset.
Definition: statistics.hpp:43
Support::Mutex m_search
Mutex for search.
Definition: engine.hh:165