/* -*- mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*- */
/*
 *  Main authors:
 *     Christian Schulte <schulte@gecode.org>
 *
 *  Copyright:
 *     Christian Schulte, 2009
 *
 *  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
 *  "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.
 *
 */

#ifndef __GECODE_SEARCH_PARALLEL_BAB_HH__
#define __GECODE_SEARCH_PARALLEL_BAB_HH__

#include <gecode/search/parallel/engine.hh>

namespace Gecode { namespace Search { namespace Parallel {

  /// %Parallel branch-and-bound engine
  class BAB : public Engine {
  protected:
    /// %Parallel branch-and-bound search worker
    class Worker : public Engine::Worker {
    protected:
      /// Number of entries not yet constrained to be better
      int mark;
      /// Best solution found so far
      Space* best;
    public:
      /// Initialize for space \a s with engine \a e
      Worker(Space* s, BAB& e);
      /// Provide access to engine
      BAB& engine(void) const;
      /// Start execution of worker
      virtual void run(void);
      /// Accept better solution \a b
      void better(Space* b);
      /// Try to find some work
      void find(void);
      /// Reset engine to restart at space \a s
      void reset(Space* s, unsigned int ngdl);
      /// Destructor
      virtual ~Worker(void);
    };
    /// Array of worker references
    Worker** _worker;
    /// Best solution so far
    Space* best;
  public:
    /// Provide access to worker \a i
    Worker* worker(unsigned int i) const;

    /// \name Search control
    //@{
    /// Report solution \a s
    void solution(Space* s);
    //@}

    /// \name Engine interface
    //@{
    /// Initialize for space \a s with options \a o
    BAB(Space* s, const Options& o);
    /// Return statistics
    virtual Statistics statistics(void) const;
    /// Reset engine to restart at space \a s
    virtual void reset(Space* s);
    /// Constrain future solutions to be better than \a b
    virtual void constrain(const Space& b);
    /// Constrain
    /// Return no-goods
    virtual NoGoods& nogoods(void);
    /// Destructor
    virtual ~BAB(void);
    //@}
  };



  /*
   * Engine: basic access routines
   */
  forceinline BAB&
  BAB::Worker::engine(void) const {
    return static_cast<BAB&>(_engine);
  }
  forceinline BAB::Worker*
  BAB::worker(unsigned int i) const {
    return _worker[i];
  }

  forceinline void
  BAB::Worker::reset(Space* s, unsigned int ngdl) {
    delete cur;
    delete best;
    best = NULL;
    path.reset((s == NULL) ? 0 : ngdl);
    d = 0;
    mark = 0;
    idle = false;
    if ((s == NULL) || (s->status(*this) == SS_FAILED)) {
      delete s;
      cur = NULL;
    } else {
      cur = s;
    }
    Search::Worker::reset();
  }


  /*
   * Engine: initialization
   */
  forceinline
  BAB::Worker::Worker(Space* s, BAB& e)
    : Engine::Worker(s,e), mark(0), best(NULL) {}

  forceinline
  BAB::BAB(Space* s, const Options& o)
    : Engine(o), best(NULL) {
    // Create workers
    _worker = static_cast<Worker**>
      (heap.ralloc(workers() * sizeof(Worker*)));
    // The first worker gets the entire search tree
    _worker[0] = new Worker(s,*this);
    // All other workers start with no work
    for (unsigned int i=1; i<workers(); i++)
      _worker[i] = new Worker(NULL,*this);
    // Block all workers
    block();
    // Create and start threads
    for (unsigned int i=0; i<workers(); i++)
      Support::Thread::run(_worker[i]);
  }


  /*
   * Engine: search control
   */
  forceinline void
  BAB::Worker::better(Space* b) {
    m.acquire();
    delete best;
    best = b->clone(false);
    mark = path.entries();
    if (cur != NULL)
      cur->constrain(*best);
    m.release();
  }
  forceinline void
  BAB::solution(Space* s) {
    m_search.acquire();
    if (best != NULL) {
      s->constrain(*best);
      if (s->status() == SS_FAILED) {
        delete s;
        m_search.release();
        return;
      } else {
        delete best;
        best = s->clone();
      }
    } else {
      best = s->clone();
    }
    // Announce better solutions
    for (unsigned int i=0; i<workers(); i++)
      worker(i)->better(best);
    bool bs = signal();
    solutions.push(s);
    if (bs)
      e_search.signal();
    m_search.release();
  }


  /*
   * Worker: finding and stealing working
   */
  forceinline void
  BAB::Worker::find(void) {
    // Try to find new work (even if there is none)
    for (unsigned int i=0; i<engine().workers(); i++) {
      unsigned long int r_d = 0ul;
      if (Space* s = engine().worker(i)->steal(r_d)) {
        // Reset this guy
        m.acquire();
        idle = false;
        // Not idle but also does not have the root of the tree
        path.ngdl(0);
        d = 0;
        cur = s;
        mark = 0;
        if (best != NULL)
          cur->constrain(*best);
        Search::Worker::reset(r_d);
        m.release();
        return;
      }
    }
  }

}}}

#endif

// STATISTICS: search-parallel
