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eqv.cpp
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4  * Christian Schulte <schulte@gecode.org>
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7  * Christian Schulte, 2011
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33 
34 #include <gecode/int/bool.hh>
35 
36 namespace Gecode { namespace Int { namespace Bool {
37 
38  /*
39  * N-ary Boolean equivalence propagator
40  *
41  */
42 
43  PropCost
44  NaryEqv::cost(const Space&, const ModEventDelta&) const {
46  }
47 
48  Actor*
50  return new (home) NaryEqv(home,*this);
51  }
52 
55  int n = x.size();
56  for (int i=n; i--; )
57  if (x[i].assigned()) {
58  pm2 ^= x[i].val();
59  x[i] = x[--n];
60  }
61  if (n == 0)
62  return (pm2 == 1) ? ES_OK : ES_FAILED;
63  if (n == 1) {
64  GECODE_ME_CHECK(x[0].eq(home,1^pm2));
65  return ES_OK;
66  }
67  if (n == 2) {
68  if (pm2 == 1) {
69  return Bool::Eq<BoolView,BoolView>::post(home,x[0],x[1]);
70  } else {
71  NegBoolView nx(x[1]);
72  return Bool::Eq<BoolView,NegBoolView>::post(home,x[0],nx);
73  }
74  }
75  x.size(n);
76  (void) new (home) NaryEqv(home,x,pm2);
77  return ES_OK;
78  }
79 
82  resubscribe(home,x0);
83  resubscribe(home,x1);
84  if (x.size() == 0) {
85  if (x0.assigned() && x1.assigned()) {
86  return (pm2 == 1) ? home.ES_SUBSUMED(*this) : ES_FAILED;
87  } else if (x0.assigned()) {
88  GECODE_ME_CHECK(x1.eq(home,1^pm2));
89  return home.ES_SUBSUMED(*this);
90  } else if (x1.assigned()) {
91  GECODE_ME_CHECK(x0.eq(home,1^pm2));
92  return home.ES_SUBSUMED(*this);
93  }
94  }
95  return ES_FIX;
96  }
97 
98 }}}
99 
100 // STATISTICS: int-prop
virtual Actor * copy(Space &home)
Copy propagator during cloning.
Definition: eqv.cpp:49
virtual PropCost cost(const Space &home, const ModEventDelta &med) const
Cost function (defined as low binary)
Definition: eqv.cpp:44
virtual ExecStatus propagate(Space &home, const ModEventDelta &med)
Perform propagation.
Definition: eqv.cpp:81
ExecStatus ES_SUBSUMED(Propagator &p)
Definition: core.hpp:3490
Negated Boolean view.
Definition: view.hpp:1574
NaryEqv(Home home, ViewArray< BoolView > &x, int pm2)
Constructor for posting.
Definition: eqv.hpp:158
static ExecStatus post(Home home, ViewArray< BoolView > &x, int pm2)
Post propagator .
Definition: eqv.cpp:54
Propagation has computed fixpoint.
Definition: core.hpp:476
Computation spaces.
Definition: core.hpp:1701
Base-class for both propagators and branchers.
Definition: core.hpp:627
ModEvent eq(Space &home, int n)
Restrict domain values to be equal to n.
Definition: bool.hpp:170
int n
Number of negative literals for node type.
Definition: bool-expr.cpp:234
static ExecStatus post(Home home, BVA x0, BVB x1)
Post propagator .
Definition: eq.hpp:60
Gecode::IntArgs i({1, 2, 3, 4})
Execution has resulted in failure.
Definition: core.hpp:473
void resubscribe(Space &home, BoolView &x0)
Update subscription.
Definition: eqv.hpp:178
#define GECODE_ME_CHECK(me)
Check whether modification event me is failed, and forward failure.
Definition: macros.hpp:52
bool assigned(void) const
Test whether view is assigned.
Definition: view.hpp:516
ExecStatus
Definition: core.hpp:471
bool assigned(View x, int v)
Whether x is assigned to value v.
Definition: single.hpp:43
ViewArray< BoolView > x
Views not yet subscribed to.
Definition: bool.hh:458
Execution is okay.
Definition: core.hpp:475
Gecode toplevel namespace
int size(void) const
Return size of array (number of elements)
Definition: array.hpp:1138
int ModEventDelta
Modification event deltas.
Definition: core.hpp:89
Home class for posting propagators
Definition: core.hpp:853
int pm2
Parity information mod 2.
Definition: bool.hh:460
static PropCost binary(PropCost::Mod m)
Two variables for modifier pcm.
Definition: core.hpp:4736