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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
* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*
*/
#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
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