int-eq.hpp

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/* -*- mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*- */
/*
 *  Main authors:
 *     Christian Schulte <schulte@gecode.org>
 *
 *  Copyright:
 *     Christian Schulte, 2006
 *
 *  Last modified:
 *     $Date: 2011-08-29 14:59:24 +0200 (Mon, 29 Aug 2011) $ by $Author: schulte $
 *     $Revision: 12359 $
 *
 *  This file is part of Gecode, the generic constraint
 *  development environment:
 *     http://www.gecode.org
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namespace Gecode { namespace Int { namespace Count {

  template<class VX, class VY>
  forceinline
  EqInt<VX,VY>::EqInt(Home home, ViewArray<VX>& x, int n_s, VY y, int c)
    : IntBase<VX,VY>(home,x,n_s,y,c) {}

  template<class VX, class VY>
  ExecStatus
  EqInt<VX,VY>::post(Home home, ViewArray<VX>& x, VY y, int c) {
    // Eliminate decided views
    int n_x = x.size();
    for (int i=n_x; i--; )
      switch (holds(x[i],y)) {
      case RT_FALSE:
        x[i] = x[--n_x]; break;
      case RT_TRUE:
        x[i] = x[--n_x]; c--; break;
      case RT_MAYBE:
        break;
      default:
        GECODE_NEVER;
      }
    x.size(n_x);
    // RHS too small or too large
    if ((c < 0) || (c > n_x))
      return ES_FAILED;
    // All views must be different
    if (c == 0)
      return post_false(home,x,y);
    // All views must be equal
    if (c == n_x)
      return post_true(home,x,y);
    // Compute how many subscriptions must be created
    int n_s = std::max(c,n_x-c)+1;
    assert(n_s <= n_x);
    (void) new (home) EqInt<VX,VY>(home,x,n_s,y,c);
    return ES_OK;
  }

  template<class VX, class VY>
  forceinline
  EqInt<VX,VY>::EqInt(Space& home, bool share, EqInt<VX,VY>& p)
    : IntBase<VX,VY>(home,share,p) {}

  template<class VX, class VY>
  Actor*
  EqInt<VX,VY>::copy(Space& home, bool share) {
    return new (home) EqInt<VX,VY>(home,share,*this);
  }

  template<class VX, class VY>
  ExecStatus
  EqInt<VX,VY>::propagate(Space& home, const ModEventDelta&) {
    // Eliminate decided views from subscribed views
    int n_x = x.size();
    for (int i=n_s; i--; )
      switch (holds(x[i],y)) {
      case RT_FALSE:
        x[i].cancel(home,*this,PC_INT_DOM);
        x[i]=x[--n_s]; x[n_s]=x[--n_x];
        break;
      case RT_TRUE:
        x[i].cancel(home,*this,PC_INT_DOM);
        x[i]=x[--n_s]; x[n_s]=x[--n_x]; c--;
        break;
      case RT_MAYBE:
        break;
      default:
        GECODE_NEVER;
      }
    x.size(n_x);
    if ((c < 0) || (c > n_x))
      return ES_FAILED;
    // Eliminate decided views from unsubscribed views
    for (int i=n_x; i-- > n_s; )
      switch (holds(x[i],y)) {
      case RT_FALSE: x[i]=x[--n_x]; break;
      case RT_TRUE:  x[i]=x[--n_x]; c--; break;
      case RT_MAYBE: break;
      default:       GECODE_NEVER;
      }
    x.size(n_x);
    if ((c < 0) || (c > n_x))
      return ES_FAILED;
    if (c == 0) {
      // All views must be different
      GECODE_ES_CHECK(post_false(home,x,y));
      return home.ES_SUBSUMED(*this);
    }
    if (c == n_x) {
      // All views must be equal
      GECODE_ES_CHECK(post_true(home,x,y));
      return home.ES_SUBSUMED(*this);
    }
    int m = std::max(c,n_x-c)+1;
    assert(m <= n_x);
    // Now, there must be new subscriptions from x[n_s] up to x[m-1]
    while (n_s < m)
      x[n_s++].subscribe(home,*this,PC_INT_DOM,false);
    return ES_FIX;
  }

}}}

// STATISTICS: int-prop