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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: 2015-03-20 15:37:34 +0100 (Fri, 20 Mar 2015) $ by $Author: schulte $
11  * $Revision: 14471 $
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, unsigned 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, unsigned int ngdl) {
116  delete cur;
117  delete best;
118  best = NULL;
119  path.reset((s == NULL) ? 0 : ngdl);
120  d = 0;
121  mark = 0;
122  idle = false;
123  if ((s == NULL) || (s->status(*this) == SS_FAILED)) {
124  delete s;
125  cur = NULL;
126  } else {
127  cur = s;
128  }
130  }
131 
132 
133  /*
134  * Engine: initialization
135  */
138  : Engine::Worker(s,e), mark(0), best(NULL) {}
139 
141  BAB::BAB(Space* s, const Options& o)
142  : Engine(o), best(NULL) {
143  // Create workers
144  _worker = static_cast<Worker**>
145  (heap.ralloc(workers() * sizeof(Worker*)));
146  // The first worker gets the entire search tree
147  _worker[0] = new Worker(s,*this);
148  // All other workers start with no work
149  for (unsigned int i=1; i<workers(); i++)
150  _worker[i] = new Worker(NULL,*this);
151  // Block all workers
152  block();
153  // Create and start threads
154  for (unsigned int i=0; i<workers(); i++)
156  }
157 
158 
159  /*
160  * Engine: search control
161  */
162  forceinline void
164  m.acquire();
165  delete best;
166  best = b->clone(false);
167  mark = path.entries();
168  if (cur != NULL)
169  cur->constrain(*best);
170  m.release();
171  }
172  forceinline void
174  m_search.acquire();
175  if (best != NULL) {
176  s->constrain(*best);
177  if (s->status() == SS_FAILED) {
178  delete s;
179  m_search.release();
180  return;
181  } else {
182  delete best;
183  best = s->clone();
184  }
185  } else {
186  best = s->clone();
187  }
188  // Announce better solutions
189  for (unsigned int i=0; i<workers(); i++)
190  worker(i)->better(best);
191  bool bs = signal();
192  solutions.push(s);
193  if (bs)
194  e_search.signal();
195  m_search.release();
196  }
197 
198 
199  /*
200  * Worker: finding and stealing working
201  */
202  forceinline void
204  // Try to find new work (even if there is none)
205  for (unsigned int i=0; i<engine().workers(); i++) {
206  unsigned long int r_d = 0ul;
207  if (Space* s = engine().worker(i)->steal(r_d)) {
208  // Reset this guy
209  m.acquire();
210  idle = false;
211  // Not idle but also does not have the root of the tree
212  path.ngdl(0);
213  d = 0;
214  cur = s;
215  mark = 0;
216  if (best != NULL)
217  cur->constrain(*best);
219  m.release();
220  return;
221  }
222  }
223  }
224 
225 }}}
226 
227 #endif
228 
229 // 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:449
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:163
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:141
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:203
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
struct Gecode::@519::NNF::@60::@61 b
For binary nodes (and, or, eqv)
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:173
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
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