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dekker.one
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, 2003
8 *
9 * This file is part of Gecode, the generic constraint
10 * development environment:
11 * http://www.gecode.org
12 *
13 * Permission is hereby granted, free of charge, to any person obtaining
14 * a copy of this software and associated documentation files (the
15 * "Software"), to deal in the Software without restriction, including
16 * without limitation the rights to use, copy, modify, merge, publish,
17 * distribute, sublicense, and/or sell copies of the Software, and to
18 * permit persons to whom the Software is furnished to do so, subject to
19 * the following conditions:
20 *
21 * The above copyright notice and this permission notice shall be
22 * included in all copies or substantial portions of the Software.
23 *
24 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
25 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
26 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
27 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
28 * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
29 * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
30 * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
31 *
32 */
33
34namespace Gecode { namespace Search { namespace Par {
35
36 /*
37 * Edge for recomputation
38 *
39 */
40 template<class Tracer>
41 forceinline
42 Path<Tracer>::Edge::Edge(void) {}
43
44 template<class Tracer>
45 forceinline
46 Path<Tracer>::Edge::Edge(Space* s, Space* c, unsigned int nid)
47 : _space(c), _alt(0), _choice(s->choice()), _nid(nid) {
48 _alt_max = _choice->alternatives()-1;
49 }
50
51 template<class Tracer>
52 forceinline Space*
53 Path<Tracer>::Edge::space(void) const {
54 return _space;
55 }
56 template<class Tracer>
57 forceinline void
58 Path<Tracer>::Edge::space(Space* s) {
59 _space = s;
60 }
61
62 template<class Tracer>
63 forceinline unsigned int
64 Path<Tracer>::Edge::alt(void) const {
65 return _alt;
66 }
67
68 template<class Tracer>
69 forceinline unsigned int
70 Path<Tracer>::Edge::nid(void) const {
71 return _nid;
72 }
73
74 template<class Tracer>
75 forceinline unsigned int
76 Path<Tracer>::Edge::truealt(void) const {
77 return std::min(_alt,_choice->alternatives()-1);
78 }
79 template<class Tracer>
80 forceinline bool
81 Path<Tracer>::Edge::rightmost(void) const {
82 return _alt >= _alt_max;
83 }
84 template<class Tracer>
85 forceinline bool
86 Path<Tracer>::Edge::lao(void) const {
87 return _alt > _alt_max;
88 }
89 template<class Tracer>
90 forceinline bool
91 Path<Tracer>::Edge::work(void) const {
92 return _alt < _alt_max;
93 }
94 template<class Tracer>
95 forceinline void
96 Path<Tracer>::Edge::next(void) {
97 _alt++;
98 }
99 template<class Tracer>
100 forceinline unsigned int
101 Path<Tracer>::Edge::steal(void) {
102 assert(work());
103 return _alt_max--;
104 }
105
106 template<class Tracer>
107 forceinline const Choice*
108 Path<Tracer>::Edge::choice(void) const {
109 return _choice;
110 }
111
112 template<class Tracer>
113 forceinline void
114 Path<Tracer>::Edge::dispose(void) {
115 delete _space;
116 delete _choice;
117 }
118
119
120
121 /*
122 * Depth-first stack with recomputation
123 *
124 */
125
126 template<class Tracer>
127 forceinline
128 Path<Tracer>::Path(unsigned int l)
129 : ds(heap), _ngdl(l), n_work(0) {}
130
131 template<class Tracer>
132 forceinline unsigned int
133 Path<Tracer>::ngdl(void) const {
134 return _ngdl;
135 }
136
137 template<class Tracer>
138 forceinline void
139 Path<Tracer>::ngdl(unsigned int l) {
140 _ngdl = l;
141 }
142
143 template<class Tracer>
144 forceinline const Choice*
145 Path<Tracer>::push(Worker& stat, Space* s, Space* c, unsigned int nid) {
146 if (!ds.empty() && ds.top().lao()) {
147 // Topmost stack entry was LAO -> reuse
148 ds.pop().dispose();
149 }
150 Edge sn(s,c,nid);
151 if (sn.work())
152 n_work++;
153 ds.push(sn);
154 stat.stack_depth(static_cast<unsigned long int>(ds.entries()));
155 return sn.choice();
156 }
157
158 template<class Tracer>
159 forceinline void
160 Path<Tracer>::next(void) {
161 while (!ds.empty())
162 if (ds.top().rightmost()) {
163 ds.pop().dispose();
164 } else {
165 assert(ds.top().work());
166 ds.top().next();
167 if (!ds.top().work())
168 n_work--;
169 return;
170 }
171 }
172
173 template<class Tracer>
174 forceinline typename Path<Tracer>::Edge&
175 Path<Tracer>::top(void) const {
176 assert(!ds.empty());
177 return ds.top();
178 }
179
180 template<class Tracer>
181 forceinline bool
182 Path<Tracer>::empty(void) const {
183 return ds.empty();
184 }
185
186 template<class Tracer>
187 forceinline void
188 Path<Tracer>::commit(Space* s, int i) const {
189 const Edge& n = ds[i];
190 s->commit(*n.choice(),n.alt());
191 }
192
193 template<class Tracer>
194 forceinline int
195 Path<Tracer>::lc(void) const {
196 int l = ds.entries()-1;
197 while (ds[l].space() == nullptr)
198 l--;
199 return l;
200 }
201
202 template<class Tracer>
203 forceinline int
204 Path<Tracer>::entries(void) const {
205 return ds.entries();
206 }
207
208 template<class Tracer>
209 forceinline void
210 Path<Tracer>::unwind(int l, Tracer& t) {
211 assert((ds[l].space() == nullptr) || ds[l].space()->failed());
212 int n = ds.entries();
213 if (t) {
214 for (int i=l; i<n; i++) {
215 Path<Tracer>::Edge& top = ds.top();
216 unsigned int fa = (i != l) ? top.alt() + 1 : top.alt();
217 for (unsigned int a = fa; a < top.choice()->alternatives(); a++) {
218 SearchTracer::EdgeInfo ei(t.wid(), top.nid(), a);
219 t.skip(ei);
220 }
221 if (ds.top().work())
222 n_work--;
223 ds.pop().dispose();
224 }
225 } else {
226 for (int i=l; i<n; i++) {
227 if (ds.top().work())
228 n_work--;
229 ds.pop().dispose();
230 }
231 }
232 assert(ds.entries() == l);
233 }
234
235 template<class Tracer>
236 forceinline void
237 Path<Tracer>::reset(unsigned int l) {
238 n_work = 0;
239 while (!ds.empty())
240 ds.pop().dispose();
241 _ngdl = l;
242 }
243
244 template<class Tracer>
245 forceinline bool
246 Path<Tracer>::steal(void) const {
247 return n_work > Config::steal_limit;
248 }
249
250 template<class Tracer>
251 forceinline Space*
252 Path<Tracer>::steal(Worker& stat, unsigned long int& d,
253 Tracer& myt, Tracer& ot) {
254 // Find position to steal: leave sufficient work
255 int n = ds.entries()-1;
256 unsigned int w = 0;
257 while (n >= 0) {
258 if (ds[n].work())
259 w++;
260 if (w > Config::steal_limit) {
261 // Okay, there is sufficient work left
262 int l=n;
263 // Find last copy
264 while (ds[l].space() == nullptr)
265 l--;
266 Space* c = ds[l].space()->clone();
267 // Recompute, if necessary
268 for (int i=l; i<n; i++)
269 commit(c,i);
270 unsigned int a = ds[n].steal();
271 c->commit(*ds[n].choice(),a);
272 if (!ds[n].work())
273 n_work--;
274 // No no-goods can be extracted above n
275 ngdl(std::min(ngdl(),static_cast<unsigned int>(n)));
276 d = stat.steal_depth(static_cast<unsigned long int>(n+1));
277 if (myt && ot) {
278 ot.ei()->init(myt.wid(),ds[n].nid(), a, *c, *ds[n].choice());
279 }
280 return c;
281 }
282 n--;
283 }
284 return nullptr;
285 }
286
287 template<class Tracer>
288 forceinline Space*
289 Path<Tracer>::recompute(unsigned int& d, unsigned int a_d, Worker& stat,
290 Tracer& t) {
291 assert(!ds.empty());
292 // Recompute space according to path
293 // Also say distance to copy (d == 0) requires immediate copying
294
295 // Check for LAO
296 if ((ds.top().space() != nullptr) && ds.top().rightmost()) {
297 Space* s = ds.top().space();
298 s->commit(*ds.top().choice(),ds.top().alt());
299 assert(ds.entries()-1 == lc());
300 ds.top().space(nullptr);
301 // Mark as reusable
302 if (static_cast<unsigned int>(ds.entries()) > ngdl())
303 ds.top().next();
304 d = 0;
305 return s;
306 }
307 // General case for recomputation
308 int l = lc(); // Position of last clone
309 int n = ds.entries(); // Number of stack entries
310 // New distance, if no adaptive recomputation
311 d = static_cast<unsigned int>(n - l);
312
313 Space* s = ds[l].space()->clone(); // Last clone
314
315 if (d < a_d) {
316 // No adaptive recomputation
317 for (int i=l; i<n; i++)
318 commit(s,i);
319 } else {
320 int m = l + static_cast<int>(d >> 1); // Middle between copy and top
321 int i = l; // To iterate over all entries
322 // Recompute up to middle
323 for (; i<m; i++ )
324 commit(s,i);
325 // Skip over all rightmost branches
326 for (; (i<n) && ds[i].rightmost(); i++)
327 commit(s,i);
328 // Is there any point to make a copy?
329 if (i<n-1) {
330 // Propagate to fixpoint
331 SpaceStatus ss = s->status(stat);
332 /*
333 * Again, the space might already propagate to failure (due to
334 * weakly monotonic propagators).
335 */
336 if (ss == SS_FAILED) {
337 // s must be deleted as it is not on the stack
338 delete s;
339 stat.fail++;
340 unwind(i,t);
341 return nullptr;
342 }
343 ds[i].space(s->clone());
344 d = static_cast<unsigned int>(n-i);
345 }
346 // Finally do the remaining commits
347 for (; i<n; i++)
348 commit(s,i);
349 }
350 return s;
351 }
352
353 template<class Tracer>
354 forceinline Space*
355 Path<Tracer>::recompute(unsigned int& d, unsigned int a_d, Worker& stat,
356 const Space& best, int& mark,
357 Tracer& t) {
358 assert(!ds.empty());
359 // Recompute space according to path
360 // Also say distance to copy (d == 0) requires immediate copying
361
362 // Check for LAO
363 if ((ds.top().space() != nullptr) && ds.top().rightmost()) {
364 Space* s = ds.top().space();
365 s->commit(*ds.top().choice(),ds.top().alt());
366 assert(ds.entries()-1 == lc());
367 if (mark > ds.entries()-1) {
368 mark = ds.entries()-1;
369 s->constrain(best);
370 }
371 ds.top().space(nullptr);
372 // Mark as reusable
373 if (static_cast<unsigned int>(ds.entries()) > ngdl())
374 ds.top().next();
375 d = 0;
376 return s;
377 }
378 // General case for recomputation
379 int l = lc(); // Position of last clone
380 int n = ds.entries(); // Number of stack entries
381 // New distance, if no adaptive recomputation
382 d = static_cast<unsigned int>(n - l);
383
384 Space* s = ds[l].space(); // Last clone
385
386 if (l < mark) {
387 mark = l;
388 s->constrain(best);
389 // The space on the stack could be failed now as an additional
390 // constraint might have been added.
391 if (s->status(stat) == SS_FAILED) {
392 // s does not need deletion as it is on the stack (unwind does this)
393 stat.fail++;
394 unwind(l,t);
395 return nullptr;
396 }
397 // It is important to replace the space on the stack with the
398 // copy: a copy might be much smaller due to flushed caches
399 // of propagators
400 Space* c = s->clone();
401 ds[l].space(c);
402 } else {
403 s = s->clone();
404 }
405
406 if (d < a_d) {
407 // No adaptive recomputation
408 for (int i=l; i<n; i++)
409 commit(s,i);
410 } else {
411 int m = l + static_cast<int>(d >> 1); // Middle between copy and top
412 int i = l; // To iterate over all entries
413 // Recompute up to middle
414 for (; i<m; i++ )
415 commit(s,i);
416 // Skip over all rightmost branches
417 for (; (i<n) && ds[i].rightmost(); i++)
418 commit(s,i);
419 // Is there any point to make a copy?
420 if (i<n-1) {
421 // Propagate to fixpoint
422 SpaceStatus ss = s->status(stat);
423 /*
424 * Again, the space might already propagate to failure
425 *
426 * This can be for two reasons:
427 * - constrain is true, so we fail
428 * - the space has weakly monotonic propagators
429 */
430 if (ss == SS_FAILED) {
431 // s must be deleted as it is not on the stack
432 delete s;
433 stat.fail++;
434 unwind(i,t);
435 return nullptr;
436 }
437 ds[i].space(s->clone());
438 d = static_cast<unsigned int>(n-i);
439 }
440 // Finally do the remaining commits
441 for (; i<n; i++)
442 commit(s,i);
443 }
444 return s;
445 }
446
447 template<class Tracer>
448 void
449 Path<Tracer>::post(Space& home) const {
450 GECODE_ES_FAIL(NoGoodsProp::post(home,*this));
451 }
452
453}}}
454
455// STATISTICS: search-par