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dfs.cpp
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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: 2013-07-12 18:20:11 +0200 (Fri, 12 Jul 2013) $ by $Author: schulte $
11  * $Revision: 13877 $
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 #include <gecode/support.hh>
39 
40 #ifdef GECODE_HAS_THREADS
41 
43 
44 namespace Gecode { namespace Search { namespace Parallel {
45 
46  /*
47  * Statistics
48  */
49  Statistics
50  DFS::statistics(void) const {
51  Statistics s;
52  for (unsigned int i=0; i<workers(); i++)
53  s += worker(i)->statistics();
54  return s;
55  }
56 
57 
58  /*
59  * Engine: search control
60  */
61  void
63  // Peform initial delay, if not first worker
64  if (this != engine().worker(0))
66  // Okay, we are in business, start working
67  while (true) {
68  switch (engine().cmd()) {
69  case C_WAIT:
70  // Wait
71  engine().wait();
72  break;
73  case C_TERMINATE:
74  // Acknowledge termination request
76  // Wait until termination can proceed
78  // Terminate thread
79  engine().terminated();
80  return;
81  case C_RESET:
82  // Acknowledge reset request
84  // Wait until reset has been performed
85  engine().wait_reset();
86  // Acknowledge that reset cycle is over
88  break;
89  case C_WORK:
90  // Perform exploration work
91  {
92  m.acquire();
93  if (idle) {
94  m.release();
95  // Try to find new work
96  find();
97  } else if (cur != NULL) {
98  start();
99  if (stop(engine().opt())) {
100  // Report stop
101  m.release();
102  engine().stop();
103  } else {
104  node++;
105  switch (cur->status(*this)) {
106  case SS_FAILED:
107  fail++;
108  delete cur;
109  cur = NULL;
110  m.release();
111  break;
112  case SS_SOLVED:
113  {
114  // Deletes all pending branchers
115  (void) cur->choice();
116  Space* s = cur->clone(false);
117  delete cur;
118  cur = NULL;
119  m.release();
120  engine().solution(s);
121  }
122  break;
123  case SS_BRANCH:
124  {
125  Space* c;
126  if ((d == 0) || (d >= engine().opt().c_d)) {
127  c = cur->clone();
128  d = 1;
129  } else {
130  c = NULL;
131  d++;
132  }
133  const Choice* ch = path.push(*this,cur,c);
134  cur->commit(*ch,0);
135  m.release();
136  }
137  break;
138  default:
139  GECODE_NEVER;
140  }
141  }
142  } else if (path.next()) {
143  cur = path.recompute(d,engine().opt().a_d,*this);
144  m.release();
145  } else {
146  idle = true;
147  path.ngdl(0);
148  m.release();
149  // Report that worker is idle
150  engine().idle();
151  }
152  }
153  break;
154  default:
155  GECODE_NEVER;
156  }
157  }
158  }
159 
160 
161  /*
162  * Perform reset
163  *
164  */
165  void
167  // Grab wait lock for reset
169  // Release workers for reset
170  release(C_RESET);
171  // Wait for reset cycle started
173  // All workers are marked as busy again
174  n_busy = workers();
175  for (unsigned int i=1; i<workers(); i++)
176  worker(i)->reset(NULL,0);
177  worker(0)->reset(s,opt().nogoods_limit);
178  // Block workers again to ensure invariant
179  block();
180  // Release reset lock
182  // Wait for reset cycle stopped
184  }
185 
186 
187 
188  /*
189  * Create no-goods
190  *
191  */
192  NoGoods&
193  DFS::nogoods(void) {
194  NoGoods* ng;
195  // Grab wait lock for reset
197  // Release workers for reset
198  release(C_RESET);
199  // Wait for reset cycle started
201  ng = &worker(0)->nogoods();
202  // Block workers again to ensure invariant
203  block();
204  // Release reset lock
206  // Wait for reset cycle stopped
208  return *ng;
209  }
210 
211 
212  /*
213  * Termination and deletion
214  */
215  DFS::~DFS(void) {
216  terminate();
217  heap.rfree(_worker);
218  }
219 
220 }}}
221 
222 #endif
223 
224 // STATISTICS: search-parallel