dfs.hh

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/* -*- 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
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 *  permit persons to whom the Software is furnished to do so, subject to
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#ifndef __GECODE_SEARCH_PARALLEL_DFS_HH__
#define __GECODE_SEARCH_PARALLEL_DFS_HH__

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

namespace Gecode { namespace Search { namespace Parallel {

  class DFS : public Engine {
  protected:
    class Worker : public Engine::Worker {
    public:
      Worker(Space* s, DFS& e);
      DFS& engine(void) const;
      virtual void run(void);
      void find(void);
      void reset(Space* s, unsigned int ngdl);
    };
    Worker** _worker;
  public:
    Worker* worker(unsigned int i) const;



    void solution(Space* s);



    DFS(Space* s, const Options& o);
    virtual Statistics statistics(void) const;
    virtual void reset(Space* s);
    virtual NoGoods& nogoods(void);
    virtual ~DFS(void);
  };


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


  /*
   * Engine: initialization
   */
  forceinline
  DFS::Worker::Worker(Space* s, DFS& e)
    : Engine::Worker(s,e) {}
  forceinline
  DFS::DFS(Space* s, const Options& o)
    : Engine(o) {
    // 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]);
  }

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


  /*
   * Engine: search control
   */
  forceinline void
  DFS::solution(Space* s) {
    m_search.acquire();
    bool bs = signal();
    solutions.push(s);
    if (bs)
      e_search.signal();
    m_search.release();
  }



  /*
   * Worker: finding and stealing working
   */
  forceinline void
  DFS::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;
        Search::Worker::reset(r_d);
        m.release();
        return;
      }
    }
  }

}}}

#endif

// STATISTICS: search-parallel