Generated on Wed Sep 3 2014 02:16:45 for Gecode by doxygen 1.8.7
dfs.cpp
Go to the documentation of this file.
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: 2013-10-24 16:42:20 +0200 (Thu, 24 Oct 2013) $ by $Author: schulte $
11  * $Revision: 14030 $
12  *
13  * This file is part of Gecode, the generic constraint
14  * development environment:
15  * http://www.gecode.org
16  *
17  * Permission is hereby granted, free of charge, to any person obtaining
18  * a copy of this software and associated documentation files (the
19  * "Software"), to deal in the Software without restriction, including
20  * without limitation the rights to use, copy, modify, merge, publish,
21  * distribute, sublicense, and/or sell copies of the Software, and to
22  * permit persons to whom the Software is furnished to do so, subject to
23  * the following conditions:
24  *
25  * The above copyright notice and this permission notice shall be
26  * included in all copies or substantial portions of the Software.
27  *
28  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
29  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
30  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
31  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
32  * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
33  * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
34  * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
35  *
36  */
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=1U; i<workers(); i++)
176  worker(i)->reset(NULL,0);
177  worker(0U)->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
Support::Event e_reset_ack_start
Event for reset acknowledgment started.
Definition: engine.hh:147
Space must be branched (at least one brancher left)
Definition: core.hpp:1266
void ack_terminate(void)
For worker to acknowledge termination command.
Definition: engine.hh:335
void wait_terminate(void)
For worker to wait until termination is legal.
Definition: engine.hh:343
void wait_reset(void)
For worker to wait for all workers to reset.
Definition: engine.hh:385
void terminate(void)
For engine to peform thread termination.
Definition: engine.hh:349
Path path
Current path ins search tree.
Definition: engine.hh:59
Search engine statistics
Definition: search.hh:136
void rfree(void *p)
Free memory block starting at p.
Definition: heap.hpp:355
Space * clone(bool share=true, CloneStatistics &stat=unused_clone) const
Clone space.
Definition: core.hpp:2777
void idle(void)
Report that worker is idle.
Definition: engine.hh:293
Statistics statistics(void)
Return statistics.
Definition: engine.hh:277
const unsigned int initial_delay
Initial delay in milliseconds for all but first worker thread.
Definition: search.hh:104
Worker * worker(unsigned int i) const
Provide access to worker i.
Definition: dfs.hh:98
void acquire(void)
Acquire the mutex and possibly block.
Definition: none.hpp:46
unsigned long int fail
Number of failed nodes in search tree.
Definition: search.hh:139
Perform reset operation.
Definition: engine.hh:94
void stop(void)
Report that worker has been stopped.
Definition: engine.hh:309
virtual void run(void)
Start execution of worker.
Definition: dfs.cpp:62
void block(void)
Block all workers.
Definition: engine.hh:222
Computation spaces.
Definition: core.hpp:1325
void find(void)
Try to find some work.
Definition: dfs.hh:165
volatile unsigned int n_busy
Number of busy workers.
Definition: engine.hh:171
Heap heap
The single global heap.
Definition: heap.cpp:49
void start(void)
Reset stop information.
Definition: worker.hh:78
void release(void)
Release the mutex.
Definition: none.hpp:52
Gecode::FloatVal c(-8, 8)
virtual NoGoods & nogoods(void)
Return no-goods.
Definition: dfs.cpp:193
void wait(void)
Ensure that worker waits.
Definition: engine.hh:232
Gecode::IntArgs i(4, 1, 2, 3, 4)
Support::Mutex m_wait_reset
Mutex for waiting for reset.
Definition: engine.hh:151
unsigned int d
Distance until next clone.
Definition: engine.hh:63
void reset(Space *s, int ngdl)
Reset worker to restart at space s.
Definition: dfs.hh:131
bool idle
Whether the worker is idle.
Definition: engine.hh:65
const unsigned int a_d
Create a clone during recomputation if distance is greater than a_d (adaptive distance) ...
Definition: search.hh:99
Cmd cmd(void) const
Return current command.
Definition: engine.hh:218
bool next(void)
Generate path for next node and return whether a next node exists.
Definition: path.hh:253
const Choice * push(Worker &stat, Space *s, Space *c)
Push space c (a clone of s or NULL)
Definition: path.hh:239
void commit(const Choice &c, unsigned int a, CommitStatistics &stat=unused_commit)
Commit choice c for alternative a.
Definition: core.hpp:2785
static void sleep(unsigned int ms)
Put current thread to sleep for ms milliseconds.
Definition: none.hpp:78
virtual void reset(Space *s)
Reset engine to restart at space s.
Definition: dfs.cpp:166
void terminated(void)
For worker to register termination.
Definition: engine.hh:323
Space * cur
Current space being explored.
Definition: engine.hh:61
unsigned int workers(void) const
Return number of workers.
Definition: engine.hh:209
const Options & opt(void) const
Provide access to search options.
Definition: engine.hh:205
Space * recompute(unsigned int &d, unsigned int a_d, Worker &s)
Recompute space according to path.
Definition: path.hh:354
virtual Statistics statistics(void) const
Return statistics.
Definition: dfs.cpp:50
int ngdl(void) const
Return no-good depth limit.
Definition: path.hh:229
void ack_reset_stop(void)
For worker to acknowledge stop of reset cycle.
Definition: engine.hh:377
void solution(Space *s)
Report solution s.
Definition: dfs.hh:150
Choice for performing commit
Definition: core.hpp:1036
No-goods recorded from restarts.
Definition: core.hpp:1240
void release(Cmd c)
Release all workers.
Definition: engine.hh:227
SpaceStatus status(StatusStatistics &stat=unused_status)
Query space status.
Definition: core.cpp:251
const unsigned int c_d
Create a clone after every c_d commits (commit distance)
Definition: search.hh:97
DFS & engine(void) const
Provide access to engine.
Definition: dfs.hh:94
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
Worker ** _worker
Array of worker references.
Definition: dfs.hh:63
Space is failed
Definition: core.hpp:1264
const Choice * choice(void)
Create new choice for current brancher.
Definition: core.cpp:365
NoGoods & nogoods(void)
Return no-goods.
Definition: engine.hh:418
void ack_reset_start(void)
For worker to acknowledge start of reset cycle.
Definition: engine.hh:369
#define GECODE_NEVER
Assert that this command is never executed.
Definition: macros.hpp:60
void wait(void)
Wait until the event becomes signalled.
Definition: none.hpp:65
bool stop(const Options &o)
Check whether engine must be stopped.
Definition: worker.hh:83
Support::Event e_reset_ack_stop
Event for reset acknowledgment stopped.
Definition: engine.hh:149
Support::Mutex m
Mutex for access to worker.
Definition: engine.hh:57
virtual ~DFS(void)
Destructor.
Definition: dfs.cpp:215
Space is solved (no brancher left)
Definition: core.hpp:1265