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link-multi.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, 2007
8  *
9  * Last modified:
10  * $Date: 2011-07-07 19:23:22 +1000 (Thu, 07 Jul 2011) $ by $Author: schulte $
11  * $Revision: 12155 $
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37 
38 #include <gecode/int/channel.hh>
39 
40 namespace Gecode { namespace Int { namespace Channel {
41 
43  class BoolIter {
44  private:
46  const ViewArray<BoolView>& x;
48  const int o;
50  int i;
51  public:
53  BoolIter(const ViewArray<BoolView>& x0, int o0);
55  bool operator ()(void) const;
57  int val(void) const;
59  void operator ++(void);
60  };
61 
64  x(x0), o(o0), i(0) {
65  while ((i<x.size()) && !x[i].zero())
66  i++;
67  }
68  forceinline bool
69  BoolIter::operator ()(void) const {
70  return i<x.size();
71  }
72  forceinline int
73  BoolIter::val(void) const {
74  assert(x[i].zero());
75  return i+o;
76  }
77  forceinline void
79  do {
80  i++;
81  } while ((i<x.size()) && !x[i].zero());
82  }
83 
84 
86  LinkMulti::LinkMulti(Space& home, bool share, LinkMulti& p)
88  (home,share,p), status(S_NONE), o(p.o) {
89  assert(p.status == S_NONE);
90  c.update(home,share,p.c);
91  }
92 
93  Actor*
94  LinkMulti::copy(Space& home, bool share) {
95  return new (home) LinkMulti(home,share,*this);
96  }
97 
98  forceinline size_t
100  Advisors<Advisor> as(c);
101  x.cancel(home,as.advisor());
102  c.dispose(home);
104  ::dispose(home);
105  return sizeof(*this);
106  }
107 
108  PropCost
109  LinkMulti::cost(const Space&, const ModEventDelta& med) const {
110  if ((status == S_ONE) || (IntView::me(med) == ME_INT_VAL))
112  else
113  return PropCost::linear(PropCost::LO, x.size());
114  }
115 
116  ExecStatus
118  if (status == S_RUN)
119  return ES_FIX;
120  // Detect a one
121  if (BoolView::one(d))
122  status = S_ONE;
123  return ES_NOFIX;
124  }
125 
126  ExecStatus
128  int n = x.size();
129 
130  // Always maintain the invariant that y lies inside the x-array
131  assert((y.min()-o >= 0) && (y.max()-o < n));
132 
133  if (y.assigned()) {
134  status = S_RUN;
135  int j=y.val()-o;
136  GECODE_ME_CHECK(x[j].one(home));
137  for (int i=0; i<j; i++)
138  GECODE_ME_CHECK(x[i].zero(home));
139  for (int i=j+1; i<n; i++)
140  GECODE_ME_CHECK(x[i].zero(home));
141  return home.ES_SUBSUMED(*this);
142  }
143 
144  // Check whether there is a one
145  if (status == S_ONE) {
146  status = S_RUN;
147  for (int i=0; true; i++)
148  if (x[i].one()) {
149  for (int j=0; j<i; j++)
150  GECODE_ME_CHECK(x[j].zero(home));
151  for (int j=i+1; j<n; j++)
152  GECODE_ME_CHECK(x[j].zero(home));
153  GECODE_ME_CHECK(y.eq(home,i+o));
154  return home.ES_SUBSUMED(*this);
155  }
156  GECODE_NEVER;
157  }
158 
159  status = S_RUN;
160 
161  redo:
162 
163  // Assign all Boolean views to zero that are outside bounds
164  {
165  int min=y.min()-o;
166  for (int i=0; i<min; i++)
167  GECODE_ME_CHECK(x[i].zero(home));
168  x.drop_fst(min); o += min; n = x.size();
169 
170  int max=y.max()-o;
171  for (int i=max+1; i<n; i++)
172  GECODE_ME_CHECK(x[i].zero(home));
173  x.drop_lst(max); n = x.size();
174  }
175 
176  {
177  // Remove zeros on the left
178  int i=0;
179  while ((i < n) && x[i].zero()) i++;
180  if (i >= n)
181  return ES_FAILED;
182  x.drop_fst(i); o += i; n = x.size();
183  }
184 
185  {
186  // Remove zeros on the right
187  int i=n-1;
188  while ((i >= 0) && x[i].zero()) i--;
189  assert(i >= 0);
190  x.drop_lst(i); n = x.size();
191  }
192 
193  assert(n >= 1);
194 
195  // Is there only one left?
196  if (n == 1) {
197  GECODE_ME_CHECK(x[0].one(home));
198  GECODE_ME_CHECK(y.eq(home,o));
199  return home.ES_SUBSUMED(*this);
200  }
201 
202  // Update bounds
203  GECODE_ME_CHECK(y.gq(home,o));
204  GECODE_ME_CHECK(y.lq(home,o+n-1));
205  if ((y.min() > o) || (y.max() < o+n-1))
206  goto redo;
207 
208  assert((n >= 2) && x[0].none() && x[n-1].none());
209  assert((y.min()-o == 0) && (y.max()-o == n-1));
210 
211  // Propagate from y to Boolean views
212  if ((IntView::me(med) == ME_INT_BND) || (IntView::me(med) == ME_INT_DOM)) {
214  int i=0;
215  do {
216  int j = v.val()-o;
217  if (i < j) {
218  GECODE_ME_CHECK(x[i].zero(home));
219  ++i;
220  } else if (i > j) {
221  ++v;
222  } else {
223  assert(i == j);
224  ++i; ++v;
225  }
226  } while (v() && (i < n));
227  }
228 
229  // Propagate from Boolean views to y
230  if (BoolView::me(med) == ME_BOOL_VAL) {
231  BoolIter bv(x,o);
232  GECODE_ME_CHECK(y.minus_v(home,bv,false));
233  }
234  status = S_NONE;
235  return ES_FIX;
236  }
237 
238 }}}
239 
240 // STATISTICS: int-prop
241