atmostOne.cpp
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/* -*- mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*- */
/*
* Main authors:
* Guido Tack <tack@gecode.org>
*
* Copyright:
* Guido Tack, 2004
*
* This file is part of Gecode, the generic constraint
* development environment:
* http://www.gecode.org
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
* LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
* OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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*
*/
#include <gecode/set/distinct.hh>
/*
* These propagators implement the scheme discussed in
*
* Andrew Sadler and Carment Gervet: Global Reasoning on Sets.
* FORMUL'01 workshop in conjunction with CP 2001.
*
* Todo: make the propagators incremental.
*/
namespace Gecode { namespace Set { namespace Distinct {
/*
* "AtMostOneIntersection" propagator
*
*/
Actor*
AtmostOne::copy(Space& home) {
return new (home) AtmostOne(home,*this);
}
ExecStatus
AtmostOne::propagate(Space& home, const ModEventDelta&) {
Region r;
LubRanges<SetView>* lubs = r.alloc<LubRanges<SetView> >(x.size());
for (int i = x.size(); i--; ) {
lubs[i].init(x[i]);
}
Iter::Ranges::NaryUnion bigT(r, lubs, x.size());
Iter::Ranges::ToValues<Iter::Ranges::NaryUnion>
as(bigT);
while (as()) {
int a = as.val(); ++as;
// cardSa is the number of sets that contain a in the glb
int cardSa = 0;
for (int i=x.size(); i--;)
if (x[i].contains(a))
cardSa++;
// bigTa is the union of all lubs that contain a
GLBndSet bigTa(home);
for (int i=x.size(); i--;) {
if (!x[i].notContains(a)) {
LubRanges<SetView> xilub(x[i]);
bigTa.includeI(home, xilub);
}
}
// maxa is the maximum number of sets that can contain a
int maxa = static_cast<int>((bigTa.size() - 1) / (c - 1));
bigTa.dispose(home);
// Conditional Rule A:
// If more sets already contain a than allowed, fail.
if (maxa < cardSa)
return ES_FAILED;
if (maxa == cardSa) {
// Conditional Rule B:
// All a used up. All other sets (those that don't have a in their
// glb already) cannot contain a.
for (int i=x.size(); i--;) {
if (!x[i].contains(a)) {
GECODE_ME_CHECK(x[i].exclude(home, a));
}
}
} else {
LubRanges<SetView>* lubs2 = r.alloc<LubRanges<SetView> >(x.size());
for (int i = x.size(); i--; ) {
lubs2[i].init(x[i]);
}
Iter::Ranges::NaryUnion bigT2(r, lubs2, x.size());
GlbRanges<SetView>* glbs = r.alloc<GlbRanges<SetView> >(cardSa);
int count = 0;
for (int i=x.size(); i--; ) {
if (x[i].contains(a)) {
glbs[count].init(x[i]);
count++;
}
}
Iter::Ranges::NaryUnion glbsa(r, glbs, cardSa);
Iter::Ranges::Diff<Iter::Ranges::NaryUnion,
Iter::Ranges::NaryUnion> deltaA(bigT2, glbsa);
Iter::Ranges::Cache deltaAC(r,deltaA);
// deltaAC contains all elements that are not yet known to be
// in a set together with a.
// Formally: \cup_i lub(x_i) - \cup_i {glb(s_i) | a\in glb(s_i)}
if (Iter::Ranges::size(deltaAC) == c - 1) {
// Conditional Rule C:
// If deltaA has exactly c-1 elements, all sets that are not yet
// known to contain a cannot contain a if it is impossible that
// they contain all of deltaA. Or the other way around:
// If a is added to the glb of a set s, deltaA must be a subset of
// s, because otherwise s would share at least one more element
// with another set that has a in its lower bound.
// Weird, eh?
for (int i=x.size(); i--; ) {
if (!x[i].contains(a) && !x[i].notContains(a)) {
deltaAC.reset();
LubRanges<SetView> xilub(x[i]);
if (!Iter::Ranges::subset(deltaAC, xilub)) {
GECODE_ME_CHECK(x[i].exclude(home, a));
}
}
}
}
}
}
return ES_NOFIX;
}
}}}
// STATISTICS: set-prop
Gecode::Iter::Ranges::Cache
Range iterator cache
Definition ranges-cache.hpp:45
Gecode::Iter::Ranges::Diff
Range iterator for computing set difference.
Definition ranges-diff.hpp:43
Gecode::Iter::Ranges::NaryUnion
Range iterator for union of iterators.
Definition ranges-union.hpp:74
Gecode::Iter::Ranges::RangeListIter::reset
void reset(void)
Reset iterator to start.
Definition ranges-list.hpp:240
Gecode::Iter::Ranges::ToValues
Value iterator from range iterator.
Definition ranges-values.hpp:42
Gecode::Iter::Ranges::ToValues::val
int val(void) const
Return current value.
Definition ranges-values.hpp:129
Gecode::NaryPropagator< SetView, PC_SET_ANY >::x
ViewArray< SetView > x
Definition pattern.hpp:145
Gecode::Propagator::Space
friend class Space
Definition core.hpp:1066
Gecode::Region
Handle to region.
Definition region.hpp:55
Gecode::Set::BndSet::size
unsigned int size(void) const
Return size.
Definition integerset.hpp:93
Gecode::Set::BndSet::dispose
void dispose(Space &home)
Free memory used by this set.
Definition integerset.hpp:60
Gecode::Set::Distinct::AtmostOne::AtmostOne
AtmostOne(Space &home, AtmostOne &p)
Constructor for cloning p.
Definition atmostOne.hpp:46
Gecode::Set::Distinct::AtmostOne::copy
virtual Actor * copy(Space &home)
Copy propagator during cloning.
Definition atmostOne.cpp:53
Gecode::Set::Distinct::AtmostOne::c
unsigned int c
Cardinality of the sets.
Definition distinct.hh:55
Gecode::Set::Distinct::AtmostOne::propagate
virtual ExecStatus propagate(Space &home, const ModEventDelta &med)
Perform propagation.
Definition atmostOne.cpp:58
Gecode::Set::GLBndSet
Growing sets of integers.
Definition var-imp.hpp:205
Gecode::Set::GLBndSet::includeI
bool includeI(Space &home, I &i)
Include the set represented by i in this set.
Definition integerset.hpp:296
Gecode::Set::GlbRanges
Range iterator for the greatest lower bound.
Definition var-imp.hpp:359
Gecode::Set::GlbRanges::init
void init(const T &x)
Initialize with greatest lower bound ranges for set variable x.
Gecode::Set::LubRanges
Range iterator for the least upper bound.
Definition var-imp.hpp:317
Gecode::Set::LubRanges::init
void init(const T &x)
Initialize with least upper bound ranges for set variable x.
Gecode::ModEventDelta
int ModEventDelta
Modification event deltas.
Definition core.hpp:89
GECODE_ME_CHECK
#define GECODE_ME_CHECK(me)
Check whether modification event me is failed, and forward failure.
Definition macros.hpp:52
Gecode::Iter::Ranges::subset
bool subset(I &i, J &j)
Check whether range iterator i is subset of range iterator j.
Definition ranges-operations.hpp:97
Gecode::Iter::Ranges::size
unsigned int size(I &i)
Size of all ranges of range iterator i.
Definition ranges-operations.hpp:74
Gecode::Set::Distinct
Propagators for global distinctness constraints.
Definition distinct.hh:39
Gecode::Set
Finite integer sets.
Definition var-imp.hpp:137
Gecode
Gecode toplevel namespace
Gecode::count
void count(Home home, const IntVarArgs &x, int n, IntRelType irt, int m, IntPropLevel ipl=IPL_DEF)
Post propagator for .
Definition count.cpp:40
Gecode::ExecStatus
ExecStatus
Definition core.hpp:472
Gecode::ES_FAILED
@ ES_FAILED
Execution has resulted in failure.
Definition core.hpp:474
Gecode::ES_NOFIX
@ ES_NOFIX
Propagation has not computed fixpoint.
Definition core.hpp:475
distinct.hh