val.hpp

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/* -*- mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*- */
/*
 *  Main authors:
 *     Patrick Pekczynski <pekczynski@ps.uni-sb.de>
 *
 *  Copyright:
 *     Patrick Pekczynski, 2005
 *
 *  Last modified:
 *     $Date: 2009-02-03 11:13:22 +0100 (Tue, 03 Feb 2009) $ by $Author: schulte $
 *     $Revision: 8129 $
 *
 *  This file is part of Gecode, the generic constraint
 *  development environment:
 *     http://www.gecode.org
 *
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 *  a copy of this software and associated documentation files (the
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namespace Gecode { namespace Int { namespace GCC {

  template <class View, class Card, bool isView>
  inline
  Val<View, Card, isView>::Val(Space& home, ViewArray<View>& x0,
                               ViewArray<Card>& k0)
    : Propagator(home), x(x0), k(k0){
    home.notice(*this,AP_DISPOSE);
    x.subscribe(home, *this, PC_INT_VAL);
    k.subscribe(home, *this, PC_INT_VAL);
  }

  template <class View, class Card, bool isView>
  forceinline
  Val<View, Card, isView>::Val(Space& home, bool share,
                               Val<View, Card, isView>& p)
    : Propagator(home,share,p) {
    x.update(home,share, p.x);
    k.update(home,share, p.k);
  }

  template <class View, class Card, bool isView>
  size_t
  Val<View, Card, isView>::dispose(Space& home) {
    home.ignore(*this,AP_DISPOSE);
    x.cancel(home,*this, PC_INT_VAL);
    k.cancel(home,*this, PC_INT_VAL);
    (void) Propagator::dispose(home);
    return sizeof(*this);
  }

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

  template <class View, class Card, bool isView>
  ExecStatus
  Val<View, Card, isView>::post(Space& home,
                                ViewArray<View>& x0,
                                ViewArray<Card>& k0) {
    new (home) Val<View, Card, isView>(home, x0, k0);
    return ES_OK;
  }

  template <class View, class Card, bool isView>
  PropCost
  Val<View, Card, isView>::cost(const Space&, const ModEventDelta&) const {
    return PropCost::linear(PropCost::HI,x.size());
  }

  template <class View, class Card, bool isView>
  ExecStatus
  Val<View, Card, isView>::propagate(Space& home, const ModEventDelta&) {
    assert(x.size() > 0);

    bool mod = false;
    int  n   = x.size();
    int  m   = k.size();

    Region r(home);
    // count[i] denotes how often value k[i].card() occurs in x
    int* count = r.alloc<int>(m);
    // stack of values having reached their maximum occurence
    int* rem = r.alloc<int>(m);
    // keep track whether a value is already on the stack
    bool* onrem = r.alloc<bool>(m);
    // stacksize
    int rs = 0;

    // initialization
    int sum_min = 0;
    int removed = 0;
    for (int i = m; i--; ) {

      removed += k[i].counter();
      sum_min += k[i].min();

      count[i] = 0;
      onrem[i] = false;
    }

    for (int i = m; i--; ) {
      // less than or equal than the total number of free variables
      // to satisfy the required occurences
      if (!k[i].assigned()) {
        int mub     = n + removed - (sum_min - k[i].min());
        ModEvent me = k[i].lq(home, mub);
        GECODE_ME_CHECK(me);
        mod |= (me_modified(me) && k[i].max() != mub);
      }
    }

    // Due to lookup operation counting requires O(n \cdot log(n)) time
    bool all_assigned = true;
    // number of assigned views with respect to the current problem size
    int  noa   = 0;
    // total number of assigned views wrt. the original probem size
    int  t_noa = 0;
    for (int i = n; i--; ) {
      bool b = x[i].assigned();
      all_assigned &= b;
      if (b) {
        int idx = lookupValue(k,x[i].val());
        if (idx == -1)
          return ES_FAILED;
        count[idx]++;
        noa++;
      }
    }

    // number of unassigned views
    int  non = x.size() - noa;

    // check for subsumption
    if (all_assigned) {

      for (int i = m; i--; ) {
        int ci = count[i] + k[i].counter();
        if (!(k[i].min() <= ci && ci <= k[i].max())) {
          return ES_FAILED;
        }
        // the solution contains ci occurences of value k[i].card();
        if (isView) {
          if (!k[i].assigned()) {
            ModEvent me = k[i].eq(home, ci);
            GECODE_ME_CHECK(me);
            mod |= k[i].assigned();
          }
        }
      }
      return ES_SUBSUMED(*this,home);
    }

    // total number of unsatisfied miminum occurences
    int req = 0;

    // number of values whose min requirements are not yet met
    int n_r = 0;

    // if only one value is unsatisified single holds the index of that value
    int single = 0;

    for (int i = m; i--; ) {
      int ci = count[i] + k[i].counter();
      t_noa += ci;
      if (ci == 0) { // this works
        req += k[i].min();
        n_r++;
        single = i;
      }

      // number of unassigned views cannot satisfy
      // the required minimum occurence
      if (req > non) {
        return ES_FAILED;
      }
    }

    // if only one unsatisfied occurences is left
    if (req == non && n_r == 1) {
      for (int i = n; i--; ) {
        // try to assign it
        if (!x[i].assigned()) {
          ModEvent me = x[i].eq(home, k[single].card());
          count[single]++;
          GECODE_ME_CHECK(me);
        }
      }
      // this might happen in case of sharing
      if (x.shared(home) && count[single] < k[single].min()) {
        count[single] = k[single].min();
      }

      for (int i = m; i--; ) {
        int ci = count[i] + k[i].counter();
        // consistency check
        if (!(k[i].min() <= ci && ci <= k[i].max())) {
          return ES_FAILED;
        }
        // the solution contains ci occurences of value k[i].card();
        if (isView) {
          if (!k[i].assigned()) {
            ModEvent me = k[i].eq(home, ci);
            GECODE_ME_CHECK(me);
          }
        }
      }
      return ES_SUBSUMED(*this,home);
    }

    for (int i = m; i--; ) {
      int ci = count[i] + k[i].counter();
      if (ci == k[i].max() && !onrem[i]) {
        rem[rs] = k[i].card();
        k[i].counter(ci);
        rs++;
        onrem[i] = true;
        if (isView) {
          // the solution contains ci occurences of value k[i].card();
          if (!k[i].assigned()) {
            ModEvent me = k[i].eq(home, ci);
            GECODE_ME_CHECK(me);
            mod |= k[i].assigned();
          }
        }
      } else {
        if (ci > k[i].max())
          return ES_FAILED;

        // in case of variable cardinalities
        if (isView) {
          if (!k[i].assigned()) {
            if (ci > k[i].min()) {
              ModEvent me = k[i].gq(home, ci);
              GECODE_ME_CHECK(me);
              mod |= k[i].assigned();
              mod |= (me_modified(me) && k[i].min() != ci);
            }
            int occupied = t_noa - ci;
            int mub = x.size() + removed - occupied;

            ModEvent me = k[i].lq(home, mub);
            GECODE_ME_CHECK(me);
            mod |= k[i].assigned();
            mod |= (me_failed(me) && k[i].max() != mub);
          }
        }
      }
      // reset counter
      count[i] = 0;
    }

    // reduce the problem size
    for (int i = n; i--; ) {
      bool b = x[i].assigned();
      if (b) {
        int idx = lookupValue(k,x[i].val());
        if (idx == -1)
          return ES_FAILED;
        if (onrem[idx]) {
          x[i] = x[--n];
          x.size(n);
        }
      }
    }

    // remove alredy satisfied values
    if (rs > 0) {
      IntSet remset(&rem[0], rs);
      for (int i = x.size(); i--;) {
        IntSetRanges rr(remset);
        if (!x[i].assigned()) {
          ModEvent me = x[i].minus_r(home, rr);
          if (me_failed(me))
            return ES_FAILED;
          mod |= x[i].assigned();
        }
      }
    }

    all_assigned = true;

    for (int i = x.size(); i--; ) {
      bool b = x[i].assigned();
      all_assigned &= b;
      if (b) {
        int idx = lookupValue(k,x[i].val());
        if (idx == -1)
          return ES_FAILED;
        count[idx]++;
      }
    }

    if (all_assigned) {
      for (int i = k.size(); i--; ) {
        int ci = count[i] + k[i].counter();
        if (!(k[i].min() <= ci && ci <= k[i].max())) {
          return ES_FAILED;
        }
        // the solution contains ci occurences of value k[i].card();
        if (isView) {
          if (!k[i].assigned()) {
            ModEvent me = k[i].eq(home, ci);
            GECODE_ME_CHECK(me);
            mod |= k[i].assigned();
          }
        }
      }
      return ES_SUBSUMED(*this,home);
    }

    if (isView) {
      // check again consistnecy of cardinalities
      int reqmin = 0;
      int allmax = 0;
      m    = k.size();
      n    = x.size();
      for (int i = m; i--; ) {
        int ci = k[i].counter();
        if (ci > k[i].max() ) {
          return ES_FAILED;
        } else {
          allmax += (k[i].max() - ci);
          if (ci < k[i].min()) {
            reqmin += (k[i].min() - ci);
          }
        }
        if (k[i].min() > n) {
          return ES_FAILED;
        }
        if (!k[i].assigned()) {
          ModEvent me = k[i].lq(home, n);
          if (me_failed(me)) {
            return ES_FAILED;
          }
        }
      }

      if (n < reqmin) {
        return ES_FAILED;
      }

      if (allmax < n) {
        return ES_FAILED;
      }
    }

    return mod ? ES_NOFIX : ES_FIX;
  }

}}}

// STATISTICS: int-prop