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#include <gecode/set.hh>#include <gecode/int.hh>
namespace Gecode { namespace Set { namespace Int {
/// Value Iterator for values above a certain weight template<class I> class OverweightValues { private: /// The threshold above which values should be iterated int threshold; /// The value iterator I iter; /// A superset of the elements found in the iterator SharedArray<int> elements; /// Weights for all the possible elements SharedArray<int> weights; /// The current index into the elements and weights int index; /// Move to the next element void next(void); public: /// \name Constructors and initialization //@{ /// Default constructor OverweightValues(void); /// Initialize with elements/weights pairs, threshold \a t and iterator \a i OverweightValues(int t, SharedArray<int>& elements0, SharedArray<int>& weights0, I& i); /// Initialize with elements/weights pairs, threshold \a t and iterator \a i void init(int t, SharedArray<int>& elements0, SharedArray<int>& weights0, I& i); //@}
/// \name Iteration control //@{ /// Test whether iterator is still at a value or done bool operator ()(void) const; /// Move iterator to next value (if possible) void operator ++(void); //@} /// \name Value access //@{ /// Return current value int val(void) const; //@} };
template<class I> forceinline void OverweightValues<I>::next(void) { while (iter()) { while (elements[index]<iter.val()) index++; assert(elements[index]==iter.val()); if (weights[index] > threshold) { return; } ++iter; } }
template<class I> forceinline OverweightValues<I>::OverweightValues(void) {}
template<class I> forceinline OverweightValues<I>::OverweightValues(int t, SharedArray<int>& elements0, SharedArray<int>& weights0, I& i) : threshold(t), iter(i), elements(elements0), weights(weights0), index(0) { next(); }
template<class I> forceinline void OverweightValues<I>::init(int t, SharedArray<int>& elements0, SharedArray<int>& weights0, I& i) { threshold = t; iter = i; elements = elements0; weights = weights0; index = 0; next(); }
template<class I> forceinline bool OverweightValues<I>::operator ()(void) const { return iter(); }
template<class I> forceinline void OverweightValues<I>::operator ++(void) { ++iter; next(); }
template<class I> forceinline int OverweightValues<I>::val(void) const { return elements[index]; }
template<class View> forceinline Weights<View>::Weights(Home home, const SharedArray<int>& elements0, const SharedArray<int>& weights0, View x0, Gecode::Int::IntView y0) : Propagator(home), elements(elements0), weights(weights0), x(x0), y(y0) { home.notice(*this,AP_DISPOSE); x.subscribe(home,*this, PC_SET_ANY); y.subscribe(home,*this, Gecode::Int::PC_INT_BND); }
template<class View> forceinline Weights<View>::Weights(Space& home, Weights& p) : Propagator(home,p), elements(p.elements), weights(p.weights) { x.update(home,p.x); y.update(home,p.y); }
template<class View> inline ExecStatus Weights<View>::post(Home home, const SharedArray<int>& elements, const SharedArray<int>& weights, View x, Gecode::Int::IntView y) { if (elements.size() != weights.size()) throw ArgumentSizeMismatch("Weights"); Region r; int* els_arr = r.alloc<int>(elements.size()); for (int i=elements.size(); i--;) els_arr[i] = elements[i]; IntSet els(els_arr, elements.size()); IntSetRanges er(els); GECODE_ME_CHECK(x.intersectI(home, er)); (void) new (home) Weights(home,elements,weights,x,y); return ES_OK; }
template<class View> PropCost Weights<View>::cost(const Space&, const ModEventDelta&) const { return PropCost::linear(PropCost::LO, y.size()+1); }
template<class View> void Weights<View>::reschedule(Space& home) { x.reschedule(home,*this, PC_SET_ANY); y.reschedule(home,*this, Gecode::Int::PC_INT_BND); }
template<class View> forceinline size_t Weights<View>::dispose(Space& home) { home.ignore(*this,AP_DISPOSE); x.cancel(home,*this, PC_SET_ANY); y.cancel(home,*this, Gecode::Int::PC_INT_BND); elements.~SharedArray(); weights.~SharedArray(); (void) Propagator::dispose(home); return sizeof(*this); }
template<class View> Actor* Weights<View>::copy(Space& home) { return new (home) Weights(home,*this); }
/// Compute the weight of the elements in the iterator \a I template<class I> forceinline int weightI(SharedArray<int>& elements, SharedArray<int>& weights, I& iter) { int sum = 0; int i = 0; Iter::Ranges::ToValues<I> v(iter); for (; v(); ++v) { // Skip all elements below the current while (elements[i]<v.val()) i++; assert(elements[i] == v.val()); sum += weights[i]; } assert(!v()); return sum; }
/// Sort order for integers class IntLess { public: bool operator ()(int x, int y); };
forceinline bool IntLess::operator ()(int x, int y) { return x < y; }
template<class View> ExecStatus Weights<View>::propagate(Space& home, const ModEventDelta&) { ModEvent me = ME_SET_NONE;
if (!x.assigned()) { // Collect the weights of the elements in the unknown set in an array int size = elements.size(); Region r; int* minWeights = r.alloc<int>(size); int* maxWeights = r.alloc<int>(size);
UnknownRanges<View> ur(x); Iter::Ranges::ToValues<UnknownRanges<View> > urv(ur); for (int i=0; i<size; i++) { if (!urv() || elements[i]<urv.val()) { minWeights[i] = INT_MAX; maxWeights[i] = INT_MIN; } else { assert(elements[i] == urv.val()); minWeights[i] = weights[i]; maxWeights[i] = weights[i]; ++urv; } }
// Sort the weights of the unknown elements IntLess il; Support::quicksort<int>(minWeights, size, il); Support::quicksort<int>(maxWeights, size, il);
// The maximum number of elements that can still be added to x int delta = static_cast<int>(std::min(x.unknownSize(), x.cardMax() - x.glbSize()));
// The weight of the elements already in x GlbRanges<View> glb(x); int glbWeight = weightI<GlbRanges<View> >(elements, weights, glb);
// Compute the weight of the current lower bound of x, plus at most // delta-1 further elements with smallest negative weights. This weight // determines which elements in the upper bound cannot possibly be // added to x (those whose weight would exceed the capacity even if // all other elements are minimal) int lowWeight = glbWeight; for (int i=0; i<delta-1; i++) { if (minWeights[i] >= 0) break; lowWeight+=minWeights[i]; }
// Compute the lowest possible weight of x. If there is another element // with negative weight left, then add its weight to lowWeight. // Otherwise lowWeight is already the lowest possible weight. int lowestWeight = lowWeight; if (delta>0 && minWeights[delta-1]<0) lowestWeight+=minWeights[delta-1];
// If after including the minimal number of required elements, // no more element with negative weight is available, then // a tighter lower bound can be computed. if ( (x.cardMin() - x.glbSize() > 0 && minWeights[x.cardMin() - x.glbSize() - 1] >= 0) || minWeights[0] >= 0 ) { int lowestPosWeight = glbWeight; for (unsigned int i=0; i<x.cardMin() - x.glbSize(); i++) { lowestPosWeight += minWeights[i]; } lowestWeight = std::max(lowestWeight, lowestPosWeight); }
// Compute the highest possible weight of x as the weight of the lower // bound plus the weight of the delta heaviest elements still in the // upper bound. int highestWeight = glbWeight; for (int i=0; i<delta; i++) { if (maxWeights[size-i-1]<=0) break; highestWeight += maxWeights[size-i-1]; }
// Prune the weight using the computed bounds GECODE_ME_CHECK(y.gq(home, lowestWeight)); GECODE_ME_CHECK(y.lq(home, highestWeight));
// Exclude all elements that are too heavy from the set x. // Elements are too heavy if their weight alone already // exceeds the remaining capacity int remainingCapacity = y.max()-lowWeight;
UnknownRanges<View> ur2(x); Iter::Ranges::ToValues<UnknownRanges<View> > urv2(ur2); OverweightValues<Iter::Ranges::ToValues<UnknownRanges<View> > > ov(remainingCapacity, elements, weights, urv2); Iter::Values::ToRanges<OverweightValues< Iter::Ranges::ToValues<UnknownRanges<View> > > > ovr(ov); me = x.excludeI(home, ovr); GECODE_ME_CHECK(me); } if (x.assigned()) { // If x is assigned, just compute its weight and assign y. GlbRanges<View> glb(x); int w = weightI<GlbRanges<View> >(elements, weights, glb); GECODE_ME_CHECK(y.eq(home, w)); return home.ES_SUBSUMED(*this); }
// return me_modified(me) ? ES_NOFIX : ES_FIX; return ES_NOFIX; }
}}}
// STATISTICS: set-prop