opt-prop.hpp

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/* -*- mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*- */
/*
 *  Main authors:
 *     Christian Schulte <schulte@gecode.org>
 *     Guido Tack <tack@gecode.org>
 *
 *  Copyright:
 *     Christian Schulte, 2009
 *     Guido Tack, 2010
 *
 *  Last modified:
 *     $Date: 2011-07-13 22:44:50 +0200 (Wed, 13 Jul 2011) $ by $Author: tack $
 *     $Revision: 12202 $
 *
 *  This file is part of Gecode, the generic constraint
 *  development environment:
 *     http://www.gecode.org
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 *  Permission is hereby granted, free of charge, to any person obtaining
 *  a copy of this software and associated documentation files (the
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 */

#include <algorithm>

namespace Gecode { namespace Int { namespace Cumulative {
  
  template<class OptTask, class Cap>
  forceinline
  OptProp<OptTask,Cap>::OptProp(Home home, Cap c0, TaskArray<OptTask>& t)
    : TaskProp<OptTask,Int::PC_INT_DOM>(home,t), c(c0) {
    c.subscribe(home,*this,PC_INT_BND);
  }

  template<class OptTask, class Cap>
  forceinline
  OptProp<OptTask,Cap>::OptProp(Space& home, bool shared,
                                OptProp<OptTask,Cap>& p) 
    : TaskProp<OptTask,Int::PC_INT_DOM>(home,shared,p) {
    c.update(home,shared,p.c);
  }

  template<class OptTask, class Cap>
  forceinline ExecStatus 
  OptProp<OptTask,Cap>::post(Home home, Cap c, TaskArray<OptTask>& t) {
    // Capacity must be nonnegative
    GECODE_ME_CHECK(c.gq(home, 0));
    // Check for overload by single task and remove excluded tasks
    int n=t.size(), m=0;
    for (int i=n; i--; ) {
      if (t[i].c() > c.max()) 
        GECODE_ME_CHECK(t[i].excluded(home));
      if (t[i].excluded())
        t[i]=t[--n];
      else if (t[i].mandatory())
        m++;
    }
    t.size(n);
    if (t.size() < 2) {
      if (t.size() == 1) {
        if (t[0].mandatory()) {
          GECODE_ME_CHECK(c.gq(home, t[0].c()));
          return ES_OK;
        } else if (c.min() >= t[0].c()) {
          return ES_OK;
        }
      } else {
        return ES_OK;
      }
    }
    if (c.assigned() && c.val()==1) {
      TaskArray<typename TaskTraits<OptTask>::UnaryTask> mt(home,t.size());
      for (int i=t.size(); i--; )
        mt[i]=t[i];
      return Unary::OptProp<typename TaskTraits<OptTask>::UnaryTask>
        ::post(home,mt);
    }
    if (m == t.size()) {
      TaskArray<typename TaskTraits<OptTask>::ManTask> mt(home,m);
      for (int i=m; i--; )
        mt[i].init(t[i]);
      return ManProp<typename TaskTraits<OptTask>::ManTask,Cap>
        ::post(home,c,mt);
    }
    (void) new (home) OptProp<OptTask,Cap>(home,c,t);
    return ES_OK;
  }

  template<class OptTask, class Cap>
  Actor* 
  OptProp<OptTask,Cap>::copy(Space& home, bool share) {
    return new (home) OptProp<OptTask,Cap>(home,share,*this);
  }

  template<class OptTask, class Cap>  
  forceinline size_t 
  OptProp<OptTask,Cap>::dispose(Space& home) {
    (void) TaskProp<OptTask,Int::PC_INT_DOM>::dispose(home);
    c.cancel(home,*this,PC_INT_BND);
    return sizeof(*this);
  }

  template<class OptTask, class Cap>
  ExecStatus 
  OptProp<OptTask,Cap>::propagate(Space& home, const ModEventDelta& med) {
    // Did one of the Boolean views change?
    if (Int::BoolView::me(med) == Int::ME_BOOL_VAL)
      GECODE_ES_CHECK((purge<OptTask,Int::PC_INT_DOM>(home,*this,t,c)));
    // Only bounds changes?
    if (Int::IntView::me(med) != Int::ME_INT_DOM)
      GECODE_ES_CHECK(overload(home,c.max(),t));

    bool subsumed;
    GECODE_ES_CHECK(basic(home,subsumed,c,t));
    if (subsumed)
      return home.ES_SUBSUMED(*this);

    // Partition into mandatory and optional activities
    int n = t.size();
    int i=0, j=n-1;
    while (true) {
      while ((i < n) && t[i].mandatory()) i++;
      while ((j >= 0) && !t[j].mandatory()) j--;
      if (i >= j) break;
      std::swap(t[i],t[j]);
    }

    if (i > 1) {
      // Truncate array to only contain mandatory tasks
      t.size(i);
      GECODE_ES_CHECK(edgefinding(home,c.max(),t));
      // Restore to also include optional tasks
      t.size(n);
    }

    if (Cap::varderived() && c.assigned() && c.val()==1) {
      // Check that tasks do not overload resource
      for (int i=t.size(); i--; )
        if (t[i].c() > 1)
          GECODE_ME_CHECK(t[i].excluded(home));
      // Rewrite to unary resource constraint
      TaskArray<typename TaskTraits<OptTask>::UnaryTask> ut(home,t.size());
      for (int i=t.size(); i--;)
        ut[i]=t[i];
      GECODE_REWRITE(*this,
        (Unary::OptProp<typename TaskTraits<OptTask>::UnaryTask>
          ::post(home(*this),ut)));
    } else {
      return ES_NOFIX;
    }
  }

}}}

// STATISTICS: int-prop