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nogoods.hpp
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3  * Main authors:
4  * Christian Schulte <schulte@gecode.org>
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7  * Christian Schulte, 2013
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33 
34 namespace Gecode { namespace Search {
35 
37  NoNGL::NoNGL(void) {}
38 
41  : NGL(home) {}
42 
44  NoNGL::NoNGL(Space& home, NoNGL& ngl)
45  : NGL(home,ngl) {}
46 
47 
48 
51  : Propagator(Home(home)), root(root0), n(0U) {
52  // Create subscriptions
53  root->subscribe(home,*this); n++;
54  bool notice = root->notice();
55  NGL* l = root->next();
56  while ((l != NULL) && l->leaf()) {
57  l->subscribe(home,*this); n++;
58  notice = notice || l->notice();
59  l = l->next();
60  }
61  if (l != NULL) {
62  l->subscribe(home,*this); n++;
63  }
64  while (!notice && (l != NULL)) {
65  notice = notice || l->notice();
66  l = l->next();
67  }
68  if (notice)
69  home.notice(*this,AP_DISPOSE);
70  }
71 
74  : Propagator(home,p), n(p.n) {
75  assert(p.root != NULL);
76  NoNGL s;
77  NGL* c = &s;
78  for (NGL* pc = p.root; pc != NULL; pc = pc->next()) {
79  NGL* n = pc->copy(home);
80  n->leaf(pc->leaf());
81  c->next(n); c=n;
82  }
83  root = s.next();
84  }
85 
86 
87 
88  template<class Path>
90  NoGoodsProp::post(Space& home, const Path& p) {
91  int s = 0;
92  int n = std::min(p.ds.entries(),static_cast<int>(p.ngdl()));
93 
94  unsigned long int n_nogood = 0;
95 
96  // Eliminate the alternatives which are not no-goods at the end
97  while ((n > s) && (p.ds[n-1].truealt() == 0U))
98  n--;
99 
100  // A sentinel element
101  NoNGL nn;
102  // Current no-good literal
103  NGL* c = &nn;
104 
105  // Commit no-goods at the beginning
106  while ((s < n) && (p.ds[s].truealt() > 0U))
107  // Try whether this is a rightmost alternative
108  if (p.ds[s].rightmost()) {
109  // No literal needed, directly try to commit
110  home.trycommit(*p.ds[s].choice(),p.ds[s].truealt());
111  s++;
112  } else {
113  // Prune using no-good literals
114  for (unsigned int a=0U; a<p.ds[s].truealt(); a++) {
115  NGL* l = home.ngl(*p.ds[s].choice(),a);
116  // Does the brancher support no-good literals?
117  if (l == NULL)
118  return ES_OK;
119  GECODE_ES_CHECK(l->prune(home));
120  }
121  // Add literal as root if needed and stop
122  if (NGL* l = home.ngl(*p.ds[s].choice(),p.ds[s].truealt())) {
123  c = c->add(l,false);
124  s++; break;
125  }
126  }
127 
128  // There are no literals
129  if (home.failed())
130  return ES_FAILED;
131  if (s >= n)
132  return ES_OK;
133 
134  // There must be at least two literals
135  assert((n-s > 1) ||
136  ((n-s == 1) && (c != &nn)));
137 
138  // Remember the last leaf
139  NGL* ll = NULL;
140 
141  // Create literals
142  for (int i=s; i<n; i++) {
143  // Add leaves
144  for (unsigned int a=0U; a<p.ds[i].truealt(); a++) {
145  NGL* l = home.ngl(*p.ds[i].choice(),a);
146  if (l == NULL) {
147  // The brancher does not support no-goods
148  if (ll == NULL)
149  return ES_OK;
150  ll->next(NULL);
151  break;
152  }
153  c = c->add(l,true); ll = c;
154  n_nogood++;
155  }
156  // Check whether to add an additional subtree
157  if (NGL* l = home.ngl(*p.ds[i].choice(),p.ds[i].truealt())) {
158  c = c->add(l,false);
159  } else if (!p.ds[i].rightmost()) {
160  // The brancher does not support no-goods
161  if (ll == NULL)
162  return ES_OK;
163  ll->next(NULL);
164  break;
165  }
166  }
167 
168  const_cast<Path&>(p).ng(n_nogood);
169 
170  (void) new (home) NoGoodsProp(home,nn.next());
171  return ES_OK;
172  }
173 
174 }}
175 
176 // STATISTICS: search-other
virtual void subscribe(Space &home, Propagator &p)=0
Subscribe propagator p to all views of the no-good literal.
NNF * l
Left subtree.
Definition: bool-expr.cpp:240
static ExecStatus post(Space &home, const Path &p)
Post propagator for path p.
Definition: nogoods.hpp:90
virtual ExecStatus prune(Space &home)=0
Propagate the negation of the no-good literal.
Actor must always be disposed.
Definition: core.hpp:561
NoNGL(void)
Constructor for creation.
Definition: nogoods.hpp:37
long long int ll(int x)
Cast x into a long long int.
Definition: mult.hpp:53
Base-class for propagators.
Definition: core.hpp:1023
#define forceinline
Definition: config.hpp:185
Computation spaces.
Definition: core.hpp:1701
NoGoodsProp(Space &home, NGL *root)
Constructor for creation.
Definition: nogoods.hpp:50
No-good propagator.
Definition: nogoods.hh:65
#define GECODE_ES_CHECK(es)
Check whether execution status es is failed or subsumed, and forward failure or subsumption.
Definition: macros.hpp:91
NGL * root
Root of no-good literal tree.
Definition: nogoods.hh:68
Gecode::FloatVal c(-8, 8)
int p
Number of positive literals for node type.
Definition: bool-expr.cpp:232
bool leaf(void) const
Test whether literal is a leaf.
Definition: core.hpp:3716
const FloatNum min
Smallest allowed float value.
Definition: float.hh:846
int n
Number of negative literals for node type.
Definition: bool-expr.cpp:234
Gecode::IntArgs i({1, 2, 3, 4})
Execution has resulted in failure.
Definition: core.hpp:473
bool failed(void) const
Check whether space is failed.
Definition: core.hpp:3971
NGL * next(void) const
Return pointer to next literal.
Definition: core.hpp:3720
void notice(Actor &a, ActorProperty p, bool duplicate=false)
Notice actor property.
Definition: core.hpp:3986
unsigned int n
Number of no-good literals with subscriptions.
Definition: nogoods.hh:70
ExecStatus
Definition: core.hpp:471
virtual bool notice(void) const
Whether dispose must always be called (returns false)
Definition: core.cpp:868
void trycommit(const Choice &c, unsigned int a, CommitStatistics &stat=unused_commit)
If possible, commit choice c for alternative a.
Definition: core.hpp:3194
Execution is okay.
Definition: core.hpp:475
NGL * add(NGL *n, bool l)
Add node n and mark it as leaf l and return n.
Definition: core.hpp:3732
Gecode toplevel namespace
Home class for posting propagators
Definition: core.hpp:853
Class for a sentinel no-good literal.
Definition: nogoods.hh:42
NGL * ngl(const Choice &c, unsigned int a)
Create no-good literal for choice c and alternative a.
Definition: core.cpp:613
struct Gecode::@593::NNF::@62::@64 a
For atomic nodes.
No-good literal recorded during search.
Definition: core.hpp:1299