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1.8.1.2
gecode
set
distinct
atmostOne.cpp
Go to the documentation of this file.
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/* -*- mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*- */
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/*
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* Main authors:
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* Guido Tack <tack@gecode.org>
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*
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* Copyright:
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* Guido Tack, 2004
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*
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* Last modified:
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* $Date: 2011-08-09 02:04:53 +1000 (Tue, 09 Aug 2011) $ by $Author: schulte $
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* $Revision: 12253 $
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*
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* This file is part of Gecode, the generic constraint
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* development environment:
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* http://www.gecode.org
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*
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* Permission is hereby granted, free of charge, to any person obtaining
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* a copy of this software and associated documentation files (the
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* "Software"), to deal in the Software without restriction, including
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* without limitation the rights to use, copy, modify, merge, publish,
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* distribute, sublicense, and/or sell copies of the Software, and to
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* permit persons to whom the Software is furnished to do so, subject to
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* the following conditions:
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*
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* The above copyright notice and this permission notice shall be
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* included in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
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* LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
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* OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*
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*/
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#include <
gecode/set/distinct.hh
>
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/*
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* These propagators implement the scheme discussed in
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*
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* Andrew Sadler and Carment Gervet: Global Reasoning on Sets.
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* FORMUL'01 workshop in conjunction with CP 2001.
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*
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* Todo: make the propagators incremental.
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*/
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namespace
Gecode {
namespace
Set {
namespace
Distinct
{
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/*
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* "AtMostOneIntersection" propagator
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*
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*/
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Actor
*
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AtmostOne::copy
(
Space
& home,
bool
share) {
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return
new
(home)
AtmostOne
(home,share,*
this
);
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}
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ExecStatus
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AtmostOne::propagate
(
Space
& home,
const
ModEventDelta
&) {
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Region
r
(home);
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LubRanges<SetView>
* lubs = r.
alloc
<
LubRanges<SetView>
>(
x
.
size
());
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for
(
int
i
=
x
.
size
();
i
--; ) {
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lubs[
i
].
init
(
x
[
i
]);
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}
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Iter::Ranges::NaryUnion
bigT(r, lubs,
x
.
size
());
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Iter::Ranges::ToValues<Iter::Ranges::NaryUnion>
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as(bigT);
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while
(as()) {
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int
a
= as.val(); ++as;
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// cardSa is the number of sets that contain a in the glb
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int
cardSa = 0;
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for
(
int
i
=
x
.
size
();
i
--;)
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if
(
x
[
i
].contains(a))
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cardSa++;
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// bigTa is the union of all lubs that contain a
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GLBndSet
bigTa(home);
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for
(
int
i
=
x
.
size
();
i
--;) {
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if
(!
x
[
i
].notContains(a)) {
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LubRanges<SetView>
xilub(
x
[
i
]);
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bigTa.
includeI
(home, xilub);
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}
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}
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// maxa is the maximum number of sets that can contain a
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int
maxa =
static_cast<
int
>
((bigTa.
size
() - 1) / (
c
- 1));
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bigTa.
dispose
(home);
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// Conditional Rule A:
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// If more sets already contain a than allowed, fail.
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if
(maxa < cardSa)
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return
ES_FAILED
;
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if
(maxa == cardSa) {
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// Conditional Rule B:
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// All a used up. All other sets (those that don't have a in their
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// glb already) cannot contain a.
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for
(
int
i
=
x
.
size
();
i
--;) {
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if
(!
x
[
i
].contains(a)) {
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GECODE_ME_CHECK
(
x
[
i
].
exclude
(home, a));
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}
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}
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}
else
{
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LubRanges<SetView>
* lubs2 = r.
alloc
<
LubRanges<SetView>
>(
x
.
size
());
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for
(
int
i
=
x
.
size
();
i
--; ) {
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lubs2[
i
].
init
(
x
[
i
]);
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}
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Iter::Ranges::NaryUnion
bigT2(r, lubs2,
x
.
size
());
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GlbRanges<SetView>
* glbs = r.
alloc
<
GlbRanges<SetView>
>(cardSa);
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int
count
= 0;
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for
(
int
i
=
x
.
size
();
i
--; ) {
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if
(
x
[
i
].contains(a)) {
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glbs[
count
].init(
x
[
i
]);
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count++;
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}
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}
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Iter::Ranges::NaryUnion
glbsa(r, glbs, cardSa);
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Iter::Ranges::Diff
<
Iter::Ranges::NaryUnion
,
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Iter::Ranges::NaryUnion> deltaA(bigT2, glbsa);
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Iter::Ranges::Cache
deltaAC(r,deltaA);
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// deltaAC contains all elements that are not yet known to be
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// in a set together with a.
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// Formally: \cup_i lub(x_i) - \cup_i {glb(s_i) | a\in glb(s_i)}
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if
(
Iter::Ranges::size
(deltaAC) ==
c
- 1) {
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// Conditional Rule C:
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// If deltaA has exactly c-1 elements, all sets that are not yet
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// known to contain a cannot contain a if it is impossible that
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// they contain all of deltaA. Or the other way around:
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// If a is added to the glb of a set s, deltaA must be a subset of
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// s, because otherwise s would share at least one more element
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// with another set that has a in its lower bound.
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// Weird, eh?
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for
(
int
i
=
x
.
size
();
i
--; ) {
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if
(!
x
[
i
].contains(a) && !
x
[
i
].notContains(a)) {
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deltaAC.
reset
();
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LubRanges<SetView>
xilub(
x
[
i
]);
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if
(!
Iter::Ranges::subset
(deltaAC, xilub)) {
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GECODE_ME_CHECK
(
x
[i].
exclude
(home, a));
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}
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}
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}
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}
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}
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}
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return
ES_NOFIX
;
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}
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}}}
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// STATISTICS: set-prop