this repo has no description
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, 2006
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 Int { namespace Linear {
35
36 /**
37 * \brief %Set for support information
38 *
39 * Records supported positions of values such that with iteration
40 * the supported values can be reconstructed.
41 *
42 */
43 class SupportSet {
44 private:
45 /// Bitset for storing support information
46 Support::BitSetBase bs;
47 public:
48 /// Default constructor
49 SupportSet(void);
50 /// Initialize support set with cardinality \a n
51 void init(Region& r, unsigned int n);
52 /// Record that there is support at position \a i
53 void support(unsigned int i);
54 /// Check whether position \arg i has support
55 bool supported(unsigned int i) const;
56
57 private:
58 /// Support-based iterator: iterates values to be removed
59 class ResultIter : public ViewValues<IntView> {
60 protected:
61 /// The support set used
62 const SupportSet& s;
63 /// The current position of the value
64 unsigned int p;
65 public:
66 /// Initialize iterator
67 ResultIter(const SupportSet& s0, const IntView& x);
68 /// Increment to next supported value
69 void operator ++(void);
70 };
71
72 public:
73 /// Perform tell according to recorded support information on \arg x
74 ModEvent tell(Space& home, IntView& x) const;
75 };
76
77 /**
78 * \brief Base-class for support-based iterator
79 *
80 */
81 template<class Val>
82 class SupportIter {
83 protected:
84 /// Integer coefficient for view
85 int a;
86 /// Integer view
87 IntView x;
88 /// Set of support for values in x
89 SupportSet s;
90 /// Current value
91 int c;
92 /// Position of current value
93 unsigned int p;
94 /// Lower bound information for value
95 Val l;
96 /// Upper bound information for value
97 Val u;
98 public:
99 /// Initialize view
100 void init(Region& r, int a, const IntView& x, Val l, Val u);
101 /// Record value at current position as supported
102 void support(void);
103 /// Tell back new variable domain according to support found
104 ModEvent tell(Space& home);
105 };
106
107
108 /**
109 * \brief Support-based iterator for positive view
110 *
111 */
112 template<class Val>
113 class PosSupportIter : public SupportIter<Val> {
114 private:
115 /// Iterate ranges of integer view in increasing order
116 IntVarImpFwd i;
117 // Using-declarations for dependant names
118 using SupportIter<Val>::a;
119 using SupportIter<Val>::x;
120 using SupportIter<Val>::s;
121 using SupportIter<Val>::c;
122 using SupportIter<Val>::p;
123 using SupportIter<Val>::l;
124 using SupportIter<Val>::u;
125 public:
126 /// Reset iterator to beginning and adjust \arg d accordingly
127 bool reset(Val& d);
128 /// Adjust \arg d and return true if next value still works
129 bool adjust(Val& d);
130 };
131
132
133 /**
134 * \brief Support-based iterator for negative view
135 *
136 */
137 template<class Val>
138 class NegSupportIter : public SupportIter<Val> {
139 private:
140 /// Iterate ranges of integer view in decreasing order
141 IntVarImpBwd i;
142 // Using-declarations for dependant names
143 using SupportIter<Val>::a;
144 using SupportIter<Val>::x;
145 using SupportIter<Val>::s;
146 using SupportIter<Val>::c;
147 using SupportIter<Val>::p;
148 using SupportIter<Val>::l;
149 using SupportIter<Val>::u;
150 public:
151 /// Reset iterator to beginning and adjust \arg d accordingly
152 bool reset(Val& d);
153 /// Adjust \arg d and return true if next value still works
154 bool adjust(Val& d);
155 };
156
157
158 /*
159 * Support set
160 *
161 */
162 forceinline
163 SupportSet::SupportSet(void) {}
164 forceinline void
165 SupportSet::init(Region& r, unsigned int n) {
166 bs.init(r,n);
167 }
168 forceinline void
169 SupportSet::support(unsigned int i) {
170 bs.set(i);
171 }
172 forceinline bool
173 SupportSet::supported(unsigned int i) const {
174 return bs.get(i);
175 }
176
177 forceinline
178 SupportSet::ResultIter::ResultIter(const SupportSet& s0, const IntView& x)
179 : ViewValues<IntView>(x), s(s0), p(0) {
180 while (ViewValues<IntView>::operator ()() && s.supported(p)) {
181 ViewValues<IntView>::operator ++(); ++p;
182 }
183 }
184 forceinline void
185 SupportSet::ResultIter::operator ++(void) {
186 do {
187 ViewValues<IntView>::operator ++(); ++p;
188 } while (ViewValues<IntView>::operator ()() && s.supported(p));
189 }
190
191
192 forceinline ModEvent
193 SupportSet::tell(Space& home, IntView& x) const {
194 switch (bs.status()) {
195 case Support::BSS_NONE:
196 return ME_INT_FAILED;
197 case Support::BSS_ALL:
198 return ME_INT_NONE;
199 case Support::BSS_SOME:
200 {
201 ResultIter i(*this,x);
202 return x.minus_v(home,i);
203 }
204 default:
205 GECODE_NEVER;
206 }
207 return ME_INT_NONE;
208 }
209
210
211 /*
212 * Base-class for support-based iterator
213 *
214 */
215 template<class Val>
216 forceinline void
217 SupportIter<Val>::init(Region& r,
218 int a0, const IntView& x0, Val l0, Val u0) {
219 a=a0; x=x0; l=l0; u=u0;
220 s.init(r,x.size());
221 }
222 template<class Val>
223 forceinline void
224 SupportIter<Val>::support(void) {
225 s.support(p);
226 }
227 template<class Val>
228 forceinline ModEvent
229 SupportIter<Val>::tell(Space& home) {
230 return s.tell(home,x);
231 }
232
233
234 /*
235 * Support-based iterator for positive view
236 *
237 */
238 template<class Val>
239 forceinline bool
240 PosSupportIter<Val>::reset(Val& d) {
241 // Way too small, no value can make it big enough
242 if (d + static_cast<Val>(a)*x.max() < u)
243 return false;
244 // Restart iterator and position of values
245 i.init(x.varimp()); p = 0;
246 // Skip all ranges which are too small
247 while (d + static_cast<Val>(a)*i.max() < u) {
248 p += i.width(); ++i;
249 }
250 // There is at least one range left (check of max)
251 assert(i());
252 // Initialize current range and adjust value
253 c = i.min();
254 // Skip all values which are too small
255 while (d + static_cast<Val>(a)*c < u) {
256 p++; c++;
257 }
258 // Adjust to new value
259 d += static_cast<Val>(a) * c;
260 return true;
261 }
262 template<class Val>
263 forceinline bool
264 PosSupportIter<Val>::adjust(Val& d) {
265 // Current value
266 Val v = static_cast<Val>(a) * c;
267 // Subtract current value from d
268 d -= v;
269 // Move to next position (number of value)
270 p++;
271 // Still in the same range
272 if (c < i.max()) {
273 // Decrement current values
274 c += 1; v += a;
275 } else {
276 // Go to next range
277 ++i;
278 if (!i())
279 return false;
280 c = i.min(); v = static_cast<Val>(a) * c;
281 }
282 // Is d with the current value too large?
283 if (d + v > l)
284 return false;
285 // Update d
286 d += v;
287 return true;
288 }
289
290
291 /*
292 * Support-based iterator for negative view
293 *
294 */
295 template<class Val>
296 forceinline bool
297 NegSupportIter<Val>::reset(Val& d) {
298 // Way too small, no value can make it big enough
299 if (d + static_cast<Val>(a)*x.min() < u)
300 return false;
301 // Restart iterator and position of values
302 i.init(x.varimp()); p = x.size()-1;
303 // Skip all ranges which are too small
304 while (d + static_cast<Val>(a)*i.min() < u) {
305 p -= i.width(); ++i;
306 }
307 // There is at least one range left (check of max)
308 assert(i());
309 // Initialize current range
310 c = i.max();
311 // Skip all values which are too small
312 while (d + static_cast<Val>(a)*c < u) {
313 p--; c--;
314 }
315 // Adjust to new value
316 d += static_cast<Val>(a) * c;
317 return true;
318 }
319 template<class Val>
320 forceinline bool
321 NegSupportIter<Val>::adjust(Val& d) {
322 // Current value
323 Val v = static_cast<Val>(a) * c;
324 // Subtract current value from d
325 d -= v;
326 // Move to next position (number of value)
327 p--;
328 // Still in the same range
329 if (c > i.min()) {
330 // Decrement current values
331 c -= 1; v -= a;
332 } else {
333 // Go to next range
334 ++i;
335 if (!i())
336 return false;
337 c = i.max(); v = static_cast<Val>(a) * c;
338 }
339 // Is d with the current value too large?
340 if (d + v > l)
341 return false;
342 // Update d
343 d += v;
344 return true;
345 }
346
347
348
349 /*
350 * The domain consisten equality propagator
351 *
352 */
353 template<class Val, class View>
354 forceinline
355 DomEq<Val,View>::DomEq(Home home,
356 ViewArray<View >& x, ViewArray<View >& y,
357 Val c)
358 : Lin<Val,View,View,PC_INT_DOM>(home,x,y,c) {}
359
360 template<class Val, class View>
361 ExecStatus
362 DomEq<Val,View>::post(Home home,
363 ViewArray<View>& x, ViewArray<View>& y,
364 Val c) {
365 (void) new (home) DomEq<Val,View>(home,x,y,c);
366 return ES_OK;
367 }
368
369 template<class Val, class View>
370 forceinline
371 DomEq<Val,View>::DomEq(Space& home, DomEq<Val,View>& p)
372 : Lin<Val,View,View,PC_INT_DOM>(home,p) {}
373
374 template<class Val, class View>
375 Actor*
376 DomEq<Val,View>::copy(Space& home) {
377 return new (home) DomEq<Val,View>(home,*this);
378 }
379
380 template<class Val, class View>
381 PropCost
382 DomEq<Val,View>::cost(const Space&, const ModEventDelta& med) const {
383 if (View::me(med) != ME_INT_DOM)
384 return PropCost::linear(PropCost::LO, x.size()+y.size());
385 else
386 return PropCost::crazy(PropCost::HI, x.size()+y.size());
387 }
388
389 template<class Val, class View>
390 ExecStatus
391 DomEq<Val,View>::propagate(Space& home, const ModEventDelta& med) {
392 if (View::me(med) != ME_INT_DOM) {
393 ExecStatus es = prop_bnd<Val,View,View>(home,med,*this,x,y,c);
394 GECODE_ES_CHECK(es);
395 return home.ES_FIX_PARTIAL(*this,View::med(ME_INT_DOM));
396 }
397
398 // Value of equation for partial assignment
399 Val d = -c;
400
401 int n = x.size();
402 int m = y.size();
403
404 Region r;
405 // Create support-base iterators
406 PosSupportIter<Val>* xp = r.alloc<PosSupportIter<Val> >(n);
407 NegSupportIter<Val>* yp = r.alloc<NegSupportIter<Val> >(m);
408
409 // Initialize views for assignments
410 {
411 Val l = 0;
412 Val u = 0;
413 for (int j=m; j--; ) {
414 yp[j].init(r,-y[j].scale(),y[j].base(),l,u);
415 l += y[j].max(); u += y[j].min();
416 }
417 for (int i=n; i--; ) {
418 xp[i].init(r,x[i].scale(),x[i].base(),l,u);
419 l -= x[i].min(); u -= x[i].max();
420 }
421 }
422
423 // Collect support information by iterating assignments
424 {
425 // Force reset of all iterators in first round
426 int i = 0;
427 int j = 0;
428
429 next_i:
430 // Reset all iterators for positive views and update d
431 while (i<n) {
432 if (!xp[i].reset(d)) goto prev_i;
433 i++;
434 }
435 next_j:
436 // Reset all iterators for negative views and update d
437 while (j<m) {
438 if (!yp[j].reset(d)) goto prev_j;
439 j++;
440 }
441 // Check whether current assignment is solution
442 if (d == 0) {
443 // Record support
444 for (int is=0; is<n; is++) xp[is].support();
445 for (int js=0; js<m; js++) yp[js].support();
446 }
447 prev_j:
448 // Try iterating to next assignment: negative views
449 while (j>0) {
450 if (yp[j-1].adjust(d)) goto next_j;
451 j--;
452 }
453 prev_i:
454 // Try iterating to next assignment: positive views
455 while (i>0) {
456 if (xp[i-1].adjust(d)) goto next_i;
457 i--;
458 }
459 }
460
461 // Tell back new variable domains
462 bool assigned = true;
463 for (int i=0; i<n; i++) {
464 GECODE_ME_CHECK(xp[i].tell(home));
465 if (!x[i].assigned())
466 assigned = false;
467 }
468 for (int j=0; j<m; j++) {
469 GECODE_ME_CHECK(yp[j].tell(home));
470 if (!y[j].assigned())
471 assigned = false;
472 }
473 if (assigned)
474 return home.ES_SUBSUMED(*this);
475 return ES_FIX;
476 }
477
478}}}
479
480// STATISTICS: int-prop