time-tabling.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, 2010
 *     Guido Tack, 2010
 *
 *  Last modified:
 *     $Date: 2016-04-19 17:19:45 +0200 (Tue, 19 Apr 2016) $ by $Author: schulte $
 *     $Revision: 14967 $
 *
 *  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
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namespace Gecode { namespace Int { namespace Cumulative {

  template<class Task>
  class TaskByDecCap {
  public:
    bool operator ()(const Task& t1, const Task& t2) const;
  };

  template<class Task>
  forceinline bool
  TaskByDecCap<Task>::operator ()(const Task& t1, const Task& t2) const {
    return t1.c() > t2.c();
  }

  // Basic propagation (timetabling)
  template<class Task, class Cap>
  forceinline ExecStatus
  timetabling(Space& home, Propagator& p, Cap c, TaskArray<Task>& t) {
    int ccur = c.max();
    int cmax = ccur;
    int cmin = ccur;

    // Sort tasks by decreasing capacity
    TaskByDecCap<Task> tbdc;
    Support::quicksort(&t[0], t.size(), tbdc);

    Region r(home);

    bool assigned;
    if (Event* e = Event::events(r,t,assigned)) {
      // Set of current but not required tasks
      Support::BitSet<Region> tasks(r,static_cast<unsigned int>(t.size()));

      // Process events, use ccur as the capacity that is still free
      do {
        // Current time
        int time = e->time();

        // Process events for completion of required part
        for ( ; (e->type() == Event::LRT) && (e->time() == time); e++)
          if (t[e->idx()].mandatory()) {
            tasks.set(static_cast<unsigned int>(e->idx()));
            ccur += t[e->idx()].c();
          }
        // Process events for completion of task
        for ( ; (e->type() == Event::LCT) && (e->time() == time); e++)
          tasks.clear(static_cast<unsigned int>(e->idx()));
        // Process events for start of task
        for ( ; (e->type() == Event::EST) && (e->time() == time); e++)
          tasks.set(static_cast<unsigned int>(e->idx()));
        // Process events for zero-length task
        for ( ; (e->type() == Event::ZRO) && (e->time() == time); e++) {
          ccur -= t[e->idx()].c();
          if (ccur < cmin) cmin=ccur;
          if (ccur < 0)
            return ES_FAILED;
          ccur += t[e->idx()].c();
        }

        // norun start time
        int nrstime = time;
        // Process events for start of required part
        for ( ; (e->type() == Event::ERT) && (e->time() == time); e++)
          if (t[e->idx()].mandatory()) {
            tasks.clear(static_cast<unsigned int>(e->idx()));
            ccur -= t[e->idx()].c();
            if (ccur < cmin) cmin=ccur;
            nrstime = time+1;
            if (ccur < 0)
              return ES_FAILED;
          } else if (t[e->idx()].optional() && (t[e->idx()].c() > ccur)) {
            GECODE_ME_CHECK(t[e->idx()].excluded(home));
          }

        // Exploit that tasks are sorted according to capacity
        for (Iter::Values::BitSet<Support::BitSet<Region> > j(tasks);
             j() && (t[j.val()].c() > ccur); ++j)
          // Task j cannot run from zltime to next time - 1
          if (t[j.val()].mandatory())
            GECODE_ME_CHECK(t[j.val()].norun(home, nrstime, e->time() - 1));
      } while (e->type() != Event::END);

      GECODE_ME_CHECK(c.gq(home,cmax-cmin));
    }

    if (assigned)
      return home.ES_SUBSUMED(p);
    return ES_NOFIX;
  }

}}}

// STATISTICS: int-prop