bnd.icc

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/* -*- mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*- */
/*
 *  Main authors:
 *     Christian Schulte <schulte@gecode.org>
 *
 *  Copyright:
 *     Christian Schulte, 2003
 *
 *  Last modified:
 *     $Date: 2008-01-31 18:29:16 +0100 (Thu, 31 Jan 2008) $ by $Author: tack $
 *     $Revision: 6017 $
 *
 *  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.
 *
 */

namespace Gecode { namespace Int { namespace Distinct {

  template <class View>
  forceinline
  Bnd<View>::Bnd(Space* home, ViewArray<View>& x0)
    : Propagator(home), x(x0), y(home,x0) {
    // Both x and y initially contain the same variables
    //  - x is used for bounds propagation
    //  - y is used for performing singleton propagation
    // They can not be shared as singleton propagation removes
    // determined variables still required for bounds propagation.
    y.subscribe(home,this,PC_INT_BND);
  }

  template <class View>
  forceinline size_t
  Bnd<View>::dispose(Space* home) {
    y.cancel(home,this,PC_INT_BND);
    (void) Propagator::dispose(home);
    return sizeof(*this);
  }

  template <class View>
  forceinline
  Bnd<View>::Bnd(Space* home, bool share, Bnd<View>& p)
    : Propagator(home,share,p) {
      x.update(home,share,p.x);
      y.update(home,share,p.y);
  }

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

  template <class View>
  PropCost
  Bnd<View>::cost(ModEventDelta med) const {
    return (View::me(med) == ME_INT_VAL)
      ? cost_lo(y.size(),PC_LINEAR_LO)
      : cost_hi(x.size(),PC_LINEAR_HI);
  }

  template <class View>
  Support::Symbol
  Bnd<View>::ati(void) {
    return Reflection::mangle<View>("Gecode::Int::Distinct::Bnd");
  }

  template <class View>
  Reflection::ActorSpec
  Bnd<View>::spec(const Space* home, Reflection::VarMap& m) const {
    Reflection::ActorSpec s(ati());
    return s << x.spec(home, m);
  }


  class Rank {
  public:
    int min, max;
  };

  template <class View>
  class MaxInc {
  protected:
    ViewArray<View> x;
  public:
    MaxInc(const ViewArray<View>& x0) : x(x0) {}
    forceinline bool
    operator()(const int i, const int j) {
      return x[i].max() < x[j].max();
    }
  };

  template <class View>
  class MinInc {
  public:
    forceinline bool
    operator()(const View& x, const View& y) {
      return x.min() < y.min();
    }
  };

  class HallInfo {
  public:
    int bounds, t, d, h;
  };

  forceinline void
  pathset_t(HallInfo hall[], int start, int end, int to) {
    int k, l;
    for (l=start; (k=l) != end; hall[k].t=to) {
      l = hall[k].t;
    }
  }

  forceinline void
  pathset_h(HallInfo hall[], int start, int end, int to) {
    int k, l;
    for (l=start; (k=l) != end; hall[k].h=to) {
      l = hall[k].h;
    }
  }

  forceinline int
  pathmin_h(const HallInfo hall[], int i) {
    while (hall[i].h < i)
      i = hall[i].h;
    return i;
  }

  forceinline int
  pathmin_t(const HallInfo hall[], int i) {
    while (hall[i].t < i)
      i = hall[i].t;
    return i;
  }

  forceinline int
  pathmax_h(const HallInfo hall[], int i) {
    while (hall[i].h > i)
      i = hall[i].h;
    return i;
  }

  forceinline int
  pathmax_t(const HallInfo hall[], int i) {
    while (hall[i].t > i)
      i = hall[i].t;
    return i;
  }

#define GECODE_INT_MINSORTED(i) (i)
#define GECODE_INT_MAXSORTED(i) (_maxsorted[i])

  template <class View>
  ExecStatus
  prop_bnd(Space* home, ViewArray<View>& x) {
    const int n = x.size();
    // Sort variable array for minimum directly
    {
      MinInc<View> min_inc;
      Support::insertion<View,MinInc<View> >(&x[0], n, min_inc);
    }

    GECODE_AUTOARRAY(int, _maxsorted, n);
    for (int i = n; i--; )
      _maxsorted[i]=i;

    {
      MaxInc<View> max_inc(x);
      Support::insertion<int,MaxInc<View> >(_maxsorted, n, max_inc);
    }

    // Setup rank and bounds info
    GECODE_AUTOARRAY(HallInfo, hall, 2*n+2);
    GECODE_AUTOARRAY(Rank,     rank, n);

    int nb = 0;
    {
      int min  = x[GECODE_INT_MINSORTED(0)].min();
      int max  = x[GECODE_INT_MAXSORTED(0)].max() + 1;
      int last = min - 2;

      hall[0].bounds = last;

      int i = 0;
      int j = 0;
      while (true) {
        if ((i < n) && (min < max)) {
          if (min != last)
            hall[++nb].bounds = last = min;
          rank[GECODE_INT_MINSORTED(i)].min = nb;
          if (++i < n)
            min = x[GECODE_INT_MINSORTED(i)].min();
        } else {
          if (max != last)
            hall[++nb].bounds = last = max;
          rank[GECODE_INT_MAXSORTED(j)].max = nb;
          if (++j == n)
            break;
          max = x[GECODE_INT_MAXSORTED(j)].max() + 1;
        }
      }
      hall[nb+1].bounds = hall[nb].bounds + 2;
    }

    // If tells cross holes, we do not compute a fixpoint
    ExecStatus es = ES_FIX;

    // Propagate lower bounds
    for (int i=nb+2; --i;) {
      hall[i].t = hall[i].h = i-1;
      hall[i].d = hall[i].bounds - hall[i-1].bounds;
    }
    for (int i=0; i<n; i++) { // visit intervals in increasing max order
      int x0 = rank[GECODE_INT_MAXSORTED(i)].min;
      int z = pathmax_t(hall, x0+1);
      int j = hall[z].t;
      if (--hall[z].d == 0)
        hall[z = pathmax_t(hall, hall[z].t=z+1)].t = j;
      pathset_t(hall, x0+1, z, z); // path compression
      int y = rank[GECODE_INT_MAXSORTED(i)].max;
      if (hall[z].d < hall[z].bounds-hall[y].bounds)
        return ES_FAILED;
      if (hall[x0].h > x0) {
        int w = pathmax_h(hall, hall[x0].h);
        int m = hall[w].bounds;
        ModEvent me = x[GECODE_INT_MAXSORTED(i)].gq(home,m);
        if (me_failed(me))
          return ES_FAILED;
        if ((me == ME_INT_VAL) || 
            ((me == ME_INT_BND) && (m != x[GECODE_INT_MAXSORTED(i)].min())))
          es = ES_NOFIX;
        pathset_h(hall, x0, w, w); // path compression
      }
      if (hall[z].d == hall[z].bounds-hall[y].bounds) {
        pathset_h(hall, hall[y].h, j-1, y); // mark hall interval
        hall[y].h = j-1;
      }
    }

    // Propagate upper bounds
    for (int i=nb+1; i--;) {
      hall[i].t = hall[i].h = i+1;
      hall[i].d = hall[i+1].bounds - hall[i].bounds;
    }
    for (int i=n; --i>=0; ) { // visit intervals in decreasing min order
      int x0 = rank[GECODE_INT_MINSORTED(i)].max;
      int z = pathmin_t(hall, x0-1);
      int j = hall[z].t;
      if (--hall[z].d == 0)
        hall[z = pathmin_t(hall, hall[z].t=z-1)].t = j;
      pathset_t(hall, x0-1, z, z);
      int y = rank[GECODE_INT_MINSORTED(i)].min;
      if (hall[z].d < hall[y].bounds-hall[z].bounds)
        return ES_FAILED;
      if (hall[x0].h < x0) {
        int w = pathmin_h(hall, hall[x0].h);
        int m = hall[w].bounds - 1;
        ModEvent me = x[GECODE_INT_MINSORTED(i)].lq(home,m);
        if (me_failed(me))
          return ES_FAILED;
        if ((me == ME_INT_VAL) || 
            ((me == ME_INT_BND) && (m != x[GECODE_INT_MAXSORTED(i)].min())))
          es = ES_NOFIX;
        pathset_h(hall, x0, w, w);
      }
      if (hall[z].d == hall[y].bounds-hall[z].bounds) {
        pathset_h(hall, hall[y].h, j+1, y);
        hall[y].h = j+1;
      }
    }

    return es;
  }

#undef GECODE_INT_MINSORTED
#undef GECODE_INT_MAXSORTED

  template <class View>
  ExecStatus
  Bnd<View>::propagate(Space* home, ModEventDelta med) {
    assert(x.size() > 1);

    if (View::me(med) == ME_INT_VAL) {
      ExecStatus es = prop_val<View,false>(home,y);
      GECODE_ES_CHECK(es);
      if (y.size() < 2)
        return ES_SUBSUMED(this,home);
      if (es == ES_FIX)
        return ES_FIX_PARTIAL(this,View::med(ME_INT_BND));
    }

    if (y.size() == 2)
      GECODE_REWRITE(this,Rel::Nq<View>::post(home,y[0],y[1]));

    ExecStatus es = prop_bnd<View>(home,x);

    GECODE_ES_CHECK(es);

    const int n = x.size();

    if ((n > 2*y.size()) && (n > 6)) {
      // If there are many assigned views, try to eliminate them
      MinInc<View> min_inc;
      Support::insertion<View,MinInc<View> >(&x[0], n, min_inc);
      int i   = 0;
      int j   = 0;
      int max = x[0].max()-1;
      while (i < n-1) {
        if (!x[i].assigned() ||
            (x[i].val() <= max) || (x[i].val() > x[i+1].min())) {
          // Keep view x[i]
          max = std::max(max,x[i].max());
          x[j++]=x[i];
        }
        i++;
      }
      if (!x[i].assigned() || (x[i].val() <= max))
        x[j++]=x[i];
      x.size(j);
    }
    
    if (x.size() < 2)
      return ES_SUBSUMED(this,home);

    if (x.size() == 2)
      GECODE_REWRITE(this,Rel::Nq<View>::post(home,x[0],x[1]));

    return es;
  }

  template <class View>
  ExecStatus
  Bnd<View>::post(Space* home, ViewArray<View>& x){
    if (x.size() == 2)
      return Rel::Nq<View>::post(home,x[0],x[1]);
    if (x.size() > 2)
      (void) new (home) Bnd<View>(home,x);
    return ES_OK;
  }

  template <class View>
  void
  Bnd<View>::post(Space* home, Reflection::VarMap& vars,
                  const Reflection::ActorSpec& spec) {
    spec.checkArity(1);
    ViewArray<View> x(home, vars, spec[0]);
    (void) new (home) Bnd<View>(home, x);
  }

}}}

// STATISTICS: int-prop