union.icc

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/* -*- mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*- */
/*
 *  Main authors:
 *     Guido Tack <tack@gecode.org>
 *     Christian Schulte <schulte@gecode.org>
 *
 *  Copyright:
 *     Guido Tack, 2004,2006
 *     Christian Schulte, 2004
 *
 *  Last modified:
 *     $Date: 2008-05-27 19:24:07 +0200 (Tue, 27 May 2008) $ by $Author: tack $
 *     $Revision: 6982 $
 *
 *  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
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 */

namespace Gecode { namespace Set { namespace Element {

  template <class SView, class RView>
  forceinline
  ElementUnion<SView,RView>::
  ElementUnion(Space* home, SView y0,
                     IdxViewArray<SView>& iv0,
                     RView y1)
    : Propagator(home), x0(y0), iv(iv0), x1(y1) {
    force(home);
    x0.subscribe(home,this, PC_SET_ANY);
    x1.subscribe(home,this, PC_SET_ANY);
    iv.subscribe(home,this, PC_SET_ANY);
  }

  template <class SView, class RView>
  forceinline
  ElementUnion<SView,RView>::
  ElementUnion(Space* home, bool share,
                     ElementUnion<SView,RView>& p)
    : Propagator(home,share,p) {
    x0.update(home,share,p.x0);
    x1.update(home,share,p.x1);
    iv.update(home,share,p.iv);
  }

  template <class SView, class RView>
  PropCost
  ElementUnion<SView,RView>::cost(ModEventDelta) const {
    return PC_LINEAR_HI;
  }

  template <class SView, class RView>
  Support::Symbol
  ElementUnion<SView,RView>::ati(void) {
    return Reflection::mangle<SView,RView>("Gecode::Set::Element::Union");
  }

  template <class SView, class RView>
  Reflection::ActorSpec
  ElementUnion<SView,RView>::spec(const Space* home,
                                 Reflection::VarMap& m) const {
    Reflection::ActorSpec s(ati());
    return s << x0.spec(home, m)
             << iv.spec(home, m)
             << x1.spec(home, m);
  }

  template <class SView, class RView>
  void
  ElementUnion<SView,RView>::post(Space* home,
                                 Reflection::VarMap& vars,
                                 const Reflection::ActorSpec& spec) {
    spec.checkArity(3);
    SView x0(home, vars, spec[0]);
    IdxViewArray<SView> iv(home, vars, spec[1]);
    RView x1(home, vars, spec[2]);
    (void) new (home) ElementUnion(home, x0, iv, x1);
  }

  template <class SView, class RView>
  size_t
  ElementUnion<SView,RView>::dispose(Space* home) {
    unforce(home);
    if (!home->failed()) {
      x0.cancel(home,this, PC_SET_ANY);
      x1.cancel(home,this, PC_SET_ANY);
      iv.cancel(home,this,PC_SET_ANY);
    }
    (void) Propagator::dispose(home);
    return sizeof(*this);
  }

  template <class SView, class RView>
  ExecStatus
  ElementUnion<SView,RView>::
  post(Space* home, SView x0, IdxViewArray<SView>& xs,
       RView x1) {
    int n = xs.size();

    // s2 \subseteq {1,...,n}
    Iter::Ranges::Singleton s(0, n-1);
    GECODE_ME_CHECK(x1.intersectI(home,s));
    (void) new (home)
      ElementUnion<SView,RView>(home,x0,xs,x1);
    return ES_OK;
  }

  template <class SView, class RView>
  Actor*
  ElementUnion<SView,RView>::copy(Space* home, bool share) {
    return new (home) ElementUnion<SView,RView>(home,share,*this);
  }

  template <class SView, class RView>
  ExecStatus
  ElementUnion<SView,RView>::propagate(Space* home, ModEventDelta) {
    int n = iv.size();

    bool loopVar;
    do {
      loopVar = false;

      // Cache the upper bound iterator, as we have to
      // modify the upper bound while iterating
      LubRanges<RView> x1ub(x1);
      Iter::Ranges::Cache<LubRanges<RView> > x1ubc(x1ub);
      Iter::Ranges::ToValues<Iter::Ranges::Cache<LubRanges<RView> > >
        vx1ub(x1ubc);

      GlbRanges<RView> x1lb(x1);
      Iter::Ranges::Cache<GlbRanges<RView> > x1lbc(x1lb);
      Iter::Ranges::ToValues<Iter::Ranges::Cache<GlbRanges<RView> > >
        vx1(x1lbc);

      // In the first iteration, compute in before[i] the union
      // of all the upper bounds of the x_i. At the same time,
      // exclude inconsistent x_i from x1 and remove them from
      // the list, cancel their dependencies.

      GLBndSet sofarBefore(home);
      LUBndSet selectedInter(home, IntSet (Limits::min,
                                   Limits::max));
      GECODE_AUTOARRAY(GLBndSet, before, n);

      int j = 0;
      int i = 0;
      
      unsigned int maxCard = 0;
      unsigned int minCard = Limits::card;
      
      while ( vx1ub() ) {

        // Remove vars at indices not in the upper bound
        if (iv[i].idx < vx1ub.val()) {
          iv[i].var.cancel(home,this, PC_SET_ANY);
          ++i;
          continue;
        }
        assert(iv[i].idx == vx1ub.val());
        iv[j] = iv[i];

        SView candidate = iv[j].var;
        int candidateInd = iv[j].idx;

        // inter = glb(candidate) & complement(lub(x0))
        GlbRanges<SView> candlb(candidate);
        LubRanges<SView> x0ub(x0);
        Iter::Ranges::Diff<GlbRanges<SView>,
          LubRanges<SView> > diff(candlb, x0ub);

        bool selectSingleInconsistent = false;
        if (x1.cardMax() <= 1) {
          GlbRanges<SView> x0lb(x0);
          LubRanges<SView> candub(candidate);
          Iter::Ranges::Diff<GlbRanges<SView>,
                             LubRanges<SView> > diff2(x0lb, candub);
          selectSingleInconsistent = diff2() || candidate.cardMax() < x0.cardMin();
        }

        // exclude inconsistent x_i
        // an x_i is inconsistent if
        //  * at most one x_i can be selected and there are
        //    elements in x_0 that can't be in x_i
        //    (selectSingleInconsistent)
        //  * its min cardinality is greater than maxCard of x0
        //  * inter is not empty (there are elements in x_i
        //    that can't be in x_0)
        if (selectSingleInconsistent ||
            candidate.cardMin() > x0.cardMax() ||
            diff()) {
          ModEvent me = (x1.exclude(home,candidateInd));
          loopVar |= me_modified(me);
          GECODE_ME_CHECK(me);

          iv[j].var.cancel(home,this, PC_SET_ANY);
          ++i;
          ++vx1ub;
          continue;
        } else {
          // if x_i is consistent, check whether we know
          // that its index is in x1
          if (vx1() && vx1.val()==candidateInd) {
            // x0 >= candidate, candidate <= x0
            GlbRanges<SView> candlb(candidate);
            ModEvent me = x0.includeI(home,candlb);
            loopVar |= me_modified(me);
            GECODE_ME_CHECK(me);

            LubRanges<SView> x0ub(x0);
            me = candidate.intersectI(home,x0ub);
            loopVar |= me_modified(me);
            GECODE_ME_CHECK(me);
            ++vx1;
          }
          new (&before[j]) GLBndSet(home);
          before[j].update(home,sofarBefore);
          LubRanges<SView> cub(candidate);
          sofarBefore.includeI(home,cub);
          GlbRanges<SView> clb(candidate);
          selectedInter.intersectI(home,clb);
          maxCard = std::max(maxCard, candidate.cardMax());
          minCard = std::min(minCard, candidate.cardMin());
        }

        ++vx1ub;
        ++i; ++j;
      }

      // cancel the variables with index greater than
      // max of lub(x1)
      for (int k=i; k<n; k++) {
        iv[k].var.cancel(home,this, PC_SET_ANY);
      }
      n = j;
      iv.size(n);

      if (x1.cardMax()==0) {
        // Selector is empty, hence the result must be empty
        {
          GECODE_ME_CHECK(x0.cardMax(home,0));
        }
        for (int i=n; i--;)
          before[i].dispose(home);
        return ES_SUBSUMED(this,home);
      }

      if (x1.cardMin() > 0) {
        // Selector is not empty, hence the intersection of the
        // possibly selected lower bounds is contained in x0
        BndSetRanges si(selectedInter);
        ModEvent me = x0.includeI(home, si);
        loopVar |= me_modified(me);
        GECODE_ME_CHECK(me);
        me = x0.cardMin(home, minCard);
        loopVar |= me_modified(me);
        GECODE_ME_CHECK(me);
      }
      selectedInter.dispose(home);

      if (x1.cardMax() <= 1) {
        ModEvent me = x0.cardMax(home, maxCard);
        loopVar |= me_modified(me);
        GECODE_ME_CHECK(me);
      }

      {
        // x0 <= sofarBefore
        BndSetRanges sfB(sofarBefore);
        ModEvent me = x0.intersectI(home,sfB);
        loopVar |= me_modified(me);
        GECODE_ME_CHECK(me);
      }

      sofarBefore.dispose(home);

      GLBndSet sofarAfter(home);

      // In the second iteration, this time backwards, compute
      // sofarAfter as the union of all lub(x_j) with j>i
      for (int i=n; i--;) {
        // TODO: check for size of universe here?
        // if (sofarAfter.size() == 0) break;
        
        // extra = inter(before[i], sofarAfter) - lub(x0)
        BndSetRanges b(before[i]);
        BndSetRanges s(sofarAfter);
        GlbRanges<SView> x0lb(x0);
        Iter::Ranges::Union<BndSetRanges, BndSetRanges> inter(b,s);
        Iter::Ranges::Diff<GlbRanges<SView>,
          Iter::Ranges::Union<BndSetRanges,BndSetRanges> > diff(x0lb, inter);
        if (diff()) {
          ModEvent me = (x1.include(home,iv[i].idx));
          loopVar |= me_modified(me);
          GECODE_ME_CHECK(me);

          // candidate != extra
          me = iv[i].var.includeI(home,diff);
          loopVar |= me_modified(me);
          GECODE_ME_CHECK(me);
        }

        LubRanges<SView> iviub(iv[i].var);
        sofarAfter.includeI(home,iviub);
        before[i].dispose(home);
      }
      sofarAfter.dispose(home);

    } while (loopVar);

    // Test whether we determined x1 without determining x0
    if (x1.assigned() && !x0.assigned()) {
      int ubsize = x1.lubSize();
      if (ubsize > 2) {
        assert(ubsize==n);
        ViewArray<SView> is(home,ubsize);
        for (int i=n; i--;)
          is[i]=iv[i].var;
        GECODE_REWRITE(this,(RelOp::UnionN<SView, SView>
                        ::post(home,is,x0)));
      } else if (ubsize == 2) {
        assert(n==2);
        SView a = iv[0].var;
        SView b = iv[1].var;
        GECODE_REWRITE(this,(RelOp::Union<SView, SView, SView>
                       ::post(home,a,b,x0)));
      } else if (ubsize == 1) {
        assert(n==1);
        GECODE_REWRITE(this,(Rel::Eq<SView,SView>::post(home,x0,iv[0].var)));
      } else {
        GECODE_ME_CHECK(x0.cardMax(home, 0));
        return ES_SUBSUMED(this,home);
      }
    }

    bool allAssigned = true;
    for (int i=iv.size(); i--;) {
      if (!iv[i].var.assigned()) {
        allAssigned = false;
        break;
      }
    }
    if (x0.assigned() && x1.assigned() && allAssigned) {
      return ES_SUBSUMED(this,home);
    }

    return ES_FIX;
  }

}}}

// STATISTICS: set-prop