On Feb 3, 2008 1:08 PM, Mikael Zayenz Lagerkvist <[EMAIL PROTECTED]> wrote:
> On 2 feb 2008, at 18.15, Didier Loiseau wrote:
> > I am trying to post a propagator for the constraint
> > x' = x or x' = epsilon
> > with x and x' integer variables and epsilon some constant not in
> > dom(x).
> If you are concerned with efficieny, then you could add a custom
> propagator for this constraint.
I realised that I actually implemented this constraint about a year
ago, and dug it out. The code below can be used to propagate "x=y |
x=z" for integer variables x, y, and z by using Extra::diseq(home, x,
y, z). I haven't tested it thoroughly, but I believe that it works.
Cheers,
Mikael
<code>
/*
* Main authors:
* Mikael Lagerkvist <[EMAIL PROTECTED]>
*
* Copyright:
* Mikael Lagerkvist, 2007
*
* 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/kernel.hh"
#include "gecode/int.hh"
#include "gecode/iter.hh"
#include "gecode/int/rel.hh"
namespace Extra {
using namespace ::Gecode;
/**
* \brief Domain-consistent propagator for \f$ x_1=x_2\lor x_1=x_3\f$.
*/
template <class View>
class DisEq : public TernaryPropagator<View,Int::PC_INT_DOM> {
protected:
using TernaryPropagator<View,Int::PC_INT_DOM>::x0;
using TernaryPropagator<View,Int::PC_INT_DOM>::x1;
using TernaryPropagator<View,Int::PC_INT_DOM>::x2;
/// Constructor for cloning \a p
DisEq(Space* home, bool share, DisEq& p);
/// Constructor for posting
DisEq(Space* home, View x0, View x1, View x2);
public:
/// Constructor for rewriting \a p during cloning
DisEq(Space* home, bool share, Propagator& p, View x0, View x1, View x2);
/// Copy propagator during cloning
virtual Actor* copy(Space* home, bool share);
/// Perform propagation
virtual ExecStatus propagate(Space* home);
/// Post propagator
static ExecStatus post(Space* home, View x0, View x1, View x2);
};
template <class View>
inline
DisEq<View>::DisEq(Space* home, View x0, View x1, View x2)
: TernaryPropagator<View,Int::PC_INT_DOM>(home,x0,x1,x2) {}
template <class View>
ExecStatus
DisEq<View>::post(Space* home, View x0, View x1, View x2) {
(void) new (home) DisEq<View>(home,x0,x1,x2);
return ES_OK;
}
template <class View>
inline
DisEq<View>::DisEq(Space* home, bool share, DisEq<View>& p)
: TernaryPropagator<View,Int::PC_INT_DOM>(home,share,p) {}
template <class View>
inline
DisEq<View>::DisEq(Space* home, bool share, Propagator& p,
View x0, View x1, View x2)
: TernaryPropagator<View,Int::PC_INT_DOM>(home,share,p,x0,x1,x2) {}
template <class View>
Actor*
DisEq<View>::copy(Space* home, bool share) {
return new (home) DisEq<View>(home,share,*this);
}
template <class View>
ExecStatus
DisEq<View>::propagate(Space* home) {
typedef Int::ViewRanges<View> Ranges;
Ranges vr1(x1), vr2(x2);
Iter::Ranges::Union<Ranges, Ranges> u12(vr1, vr2);
GECODE_ME_CHECK(x1.inter_r(home, u12, false));
if (rtest_nq_dom(x0, x1) == Int::RT_TRUE)
GECODE_REWRITE(this,
(Int::Rel::EqDom<View, View>::post(home, x0, x2)));
if (rtest_nq_dom(x0, x2) == Int::RT_TRUE)
GECODE_REWRITE(this,
(Int::Rel::EqDom<View, View>::post(home, x0, x1)));
return x0.assigned() && (x1.assigned() || x2.assigned()) ?
ES_SUBSUMED(this,home) : ES_FIX;
}
/** \brief Post propagator for \f$ x_1=x_2\lor x_1=x_3\f$
*/
void diseq(Space* home, IntVar x1, IntVar x2, IntVar x3) {
Int::IntView v1(x1), v2(x2), v3(x3);
GECODE_ES_FAIL(home,DisEq<Int::IntView>::post(home, v1, v2, v3));
}
}
</code>
--
Mikael Zayenz Lagerkvist, http://www.ict.kth.se/~zayenz/
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