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dfs.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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15  * http://www.gecode.org
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37 
38 #ifndef __GECODE_SEARCH_PARALLEL_DFS_HH__
39 #define __GECODE_SEARCH_PARALLEL_DFS_HH__
40 
42 
43 namespace Gecode { namespace Search { namespace Parallel {
44 
46  class DFS : public Engine {
47  protected:
49  class Worker : public Engine::Worker {
50  public:
52  Worker(Space* s, DFS& e);
54  DFS& engine(void) const;
56  virtual void run(void);
58  void find(void);
60  void reset(Space* s, int ngdl);
61  };
64  public:
66  Worker* worker(unsigned int i) const;
67 
69 
70  void solution(Space* s);
73 
75 
76  DFS(Space* s, const Options& o);
79  virtual Statistics statistics(void) const;
81  virtual void reset(Space* s);
83  virtual NoGoods& nogoods(void);
85  virtual ~DFS(void);
87  };
88 
89 
90  /*
91  * Basic access routines
92  */
94  DFS::Worker::engine(void) const {
95  return static_cast<DFS&>(_engine);
96  }
98  DFS::worker(unsigned int i) const {
99  return _worker[i];
100  }
101 
102 
103  /*
104  * Engine: initialization
105  */
108  : Engine::Worker(s,e) {}
110  DFS::DFS(Space* s, const Options& o)
111  : Engine(o) {
112  // Create workers
113  _worker = static_cast<Worker**>
114  (heap.ralloc(workers() * sizeof(Worker*)));
115  // The first worker gets the entire search tree
116  _worker[0] = new Worker(s,*this);
117  // All other workers start with no work
118  for (unsigned int i=1; i<workers(); i++)
119  _worker[i] = new Worker(NULL,*this);
120  // Block all workers
121  block();
122  // Create and start threads
123  for (unsigned int i=0; i<workers(); i++)
125  }
126 
127  /*
128  * Reset
129  */
130  forceinline void
131  DFS::Worker::reset(Space* s, int ngdl) {
132  delete cur;
133  path.reset((s != NULL) ? ngdl : 0);
134  d = 0;
135  idle = false;
136  if ((s == NULL) || (s->status(*this) == SS_FAILED)) {
137  delete s;
138  cur = NULL;
139  } else {
140  cur = s;
141  }
143  }
144 
145 
146  /*
147  * Engine: search control
148  */
149  forceinline void
151  m_search.acquire();
152  bool bs = signal();
153  solutions.push(s);
154  if (bs)
155  e_search.signal();
156  m_search.release();
157  }
158 
159 
160 
161  /*
162  * Worker: finding and stealing working
163  */
164  forceinline void
166  // Try to find new work (even if there is none)
167  for (unsigned int i=0; i<engine().workers(); i++) {
168  unsigned long int r_d = 0ul;
169  if (Space* s = engine().worker(i)->steal(r_d)) {
170  // Reset this guy
171  m.acquire();
172  idle = false;
173  // Not idle but also does not have the root of the tree
174  path.ngdl(0);
175  d = 0;
176  cur = s;
178  m.release();
179  return;
180  }
181  }
182  }
183 
184 }}}
185 
186 #endif
187 
188 // STATISTICS: search-parallel