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eqv.cpp
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3  * Main authors:
4  * Christian Schulte <schulte@gecode.org>
5  *
6  * Copyright:
7  * Christian Schulte, 2011
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10  * $Date: 2011-10-07 11:28:27 +0200 (Fri, 07 Oct 2011) $ by $Author: schulte $
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37 
38 #include <gecode/int/bool.hh>
39 
40 namespace Gecode { namespace Int { namespace Bool {
41 
42  /*
43  * N-ary Boolean equivalence propagator
44  *
45  */
46 
47  PropCost
48  NaryEqv::cost(const Space&, const ModEventDelta&) const {
50  }
51 
52  Actor*
53  NaryEqv::copy(Space& home, bool share) {
54  return new (home) NaryEqv(home,share,*this);
55  }
56 
59  int n = x.size();
60  for (int i=n; i--; )
61  if (x[i].assigned()) {
62  pm2 ^= x[i].val();
63  x[i] = x[--n];
64  }
65  if (n == 0)
66  return (pm2 == 1) ? ES_OK : ES_FAILED;
67  if (n == 1) {
68  GECODE_ME_CHECK(x[0].eq(home,1^pm2));
69  return ES_OK;
70  }
71  if (n == 2) {
72  if (pm2 == 1) {
73  return Bool::Eq<BoolView,BoolView>::post(home,x[0],x[1]);
74  } else {
75  NegBoolView n(x[1]);
76  return Bool::Eq<BoolView,NegBoolView>::post(home,x[0],n);
77  }
78  }
79  x.size(n);
80  (void) new (home) NaryEqv(home,x,pm2);
81  return ES_OK;
82  }
83 
86  resubscribe(home,x0);
87  resubscribe(home,x1);
88  if (x.size() == 0) {
89  if (x0.assigned() && x1.assigned()) {
90  return (pm2 == 1) ? home.ES_SUBSUMED(*this) : ES_FAILED;
91  } else if (x0.assigned()) {
92  GECODE_ME_CHECK(x1.eq(home,1^pm2));
93  return home.ES_SUBSUMED(*this);
94  } else if (x1.assigned()) {
95  GECODE_ME_CHECK(x0.eq(home,1^pm2));
96  return home.ES_SUBSUMED(*this);
97  }
98  }
99  return ES_FIX;
100  }
101 
102 }}}
103 
104 // STATISTICS: int-prop
virtual ExecStatus propagate(Space &home, const ModEventDelta &med)
Perform propagation.
Definition: eqv.cpp:85
ExecStatus ES_SUBSUMED(Propagator &p)
Definition: core.hpp:2973
Negated Boolean view.
Definition: view.hpp:1503
NaryEqv(Home home, ViewArray< BoolView > &x, int pm2)
Constructor for posting.
Definition: eqv.hpp:162
static ExecStatus post(Home home, ViewArray< BoolView > &x, int pm2)
Post propagator .
Definition: eqv.cpp:58
Propagation has computed fixpoint.
Definition: core.hpp:528
Computation spaces.
Definition: core.hpp:1362
Base-class for both propagators and branchers.
Definition: core.hpp:666
ModEvent eq(Space &home, int n)
Restrict domain values to be equal to n.
Definition: bool.hpp:164
Gecode::IntArgs i(4, 1, 2, 3, 4)
int n
Number of negative literals for node type.
Definition: bool-expr.cpp:238
static ExecStatus post(Home home, BVA x0, BVB x1)
Post propagator .
Definition: eq.hpp:64
virtual PropCost cost(const Space &home, const ModEventDelta &med) const
Cost function (defined as low binary)
Definition: eqv.cpp:48
Execution has resulted in failure.
Definition: core.hpp:525
void resubscribe(Space &home, BoolView &x0)
Update subscription.
Definition: eqv.hpp:182
virtual Actor * copy(Space &home, bool share)
Copy propagator during cloning.
Definition: eqv.cpp:53
#define GECODE_ME_CHECK(me)
Check whether modification event me is failed, and forward failure.
Definition: macros.hpp:45
Node * x
Pointer to corresponding Boolean expression node.
Definition: bool-expr.cpp:253
ExecStatus
Definition: core.hpp:523
bool assigned(View x, int v)
Whether x is assigned to value v.
Definition: single.hpp:47
bool assigned(void) const
Test whether view is assigned.
Definition: view.hpp:448
ViewArray< BoolView > x
Views not yet subscribed to.
Definition: bool.hh:456
Execution is okay.
Definition: core.hpp:527
int size(void) const
Return size of array (number of elements)
Definition: array.hpp:1215
Gecode toplevel namespace
int ModEventDelta
Modification event deltas.
Definition: core.hpp:173
Home class for posting propagators
Definition: core.hpp:717
int pm2
Parity information mod 2.
Definition: bool.hh:458
static PropCost binary(PropCost::Mod m)
Two variables for modifier pcm.
Definition: core.hpp:4054