text: /* -*- mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*- */
  /*
   *  Main authors:
   *     Christian Schulte <schulte@gecode.org>
   *
   *  Contributing authors:
   *     Guido Tack <tack@gecode.org>
   *
   *  Copyright:
   *     Christian Schulte, 2004
   *     Guido Tack, 2004
   *
   *  Last modified:
   *     $Date: 2013-10-24 16:42:20 +0200 (to, 24 okt 2013) $ by $Author: schulte $
   *     $Revision: 14030 $
   *
   *  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_SEQUENTIAL_BAB_HH__
  #define __GECODE_SEARCH_SEQUENTIAL_BAB_HH__
  
  #include <gecode/search.hh>
  #include <gecode/search/support.hh>
  #include <gecode/search/worker.hh>
  #include <gecode/search/sequential/path.hh>
  
  namespace Gecode { namespace Search { namespace Sequential {
  
    /// Implementation of depth-first branch-and-bound search engine
    class BAB : public Worker {
    private:
      /// Search options
      Options opt;
      /// Current path in search tree
      Path path;
      /// Current space being explored
      Space* cur;
      /// Distance until next clone
      unsigned int d;
      /// Number of entries not yet constrained to be better
      int mark;
      /// Best solution found so far
      Space* best;
    public:
      /// Initialize with space \a s and search options \a o
      BAB(Space* s, const Options& o);
      /// %Search for next better solution
      Space* next(void);
      /// Return statistics
      Statistics statistics(void) const;
      /// Reset engine to restart at space \a s
      void reset(Space* s);
      /// Return no-goods
      NoGoods& nogoods(void);
      /// Destructor
      ~BAB(void);
    };
  
    forceinline 
    BAB::BAB(Space* s, const Options& o)
      : opt(o), path(static_cast<int>(opt.nogoods_limit)), 
        d(0), mark(0), best(NULL) {
      if ((s == NULL) || (s->status(*this) == SS_FAILED)) {
        fail++;
        cur = NULL;
        if (!o.clone)
          delete s;
      } else {
        cur = snapshot(s,opt);
      }
    }
  
    forceinline Space*
    BAB::next(void) {
      /*
       * The invariant maintained by the engine is:
       *   For all nodes stored at a depth less than mark, there
       *   is no guarantee of betterness. For those above the mark,
       *   betterness is guaranteed.
       *
       * The engine maintains the path on the stack for the current
       * node to be explored.
       *
       */
      start();
      while (true) {
        while (cur) {
          if (stop(opt))
            return NULL;
          node++;
          switch (cur->status(*this)) {
          case SS_FAILED:
            fail++;
            delete cur;
            cur = NULL;
            break;
          case SS_SOLVED:
            // Deletes all pending branchers
            (void) cur->choice();
            delete best;
            best = cur;
            cur = NULL;
            mark = path.entries();
            return best->clone();
          case SS_BRANCH:
            {
              Space* c;
              if ((d == 0) || (d >= opt.c_d)) {
                c = cur->clone();
                d = 1;
              } else {
                c = NULL;
                d++;
              }
              const Choice* ch = path.push(*this,cur,c);
              cur->commit(*ch,0);
              break;
            }
          default:
            GECODE_NEVER;
          }
        }
        // Recompute and add constraint if necessary
        do {
          if (!path.next())
            return NULL;
          cur = path.recompute(d,opt.a_d,*this,best,mark);
        } while (cur == NULL);
      }
      GECODE_NEVER;
      return NULL;
    }
  
    forceinline Statistics
    BAB::statistics(void) const {
      return *this;
    }
  
    forceinline void
    BAB::reset(Space* s) { 
      delete best;
      best = NULL;
      path.reset();
      d = mark = 0U;
      delete cur;
      if ((s == NULL) || (s->status(*this) == SS_FAILED)) {
        cur = NULL;
      } else {
        cur = s;
      }
      Worker::reset();
    }
  
    forceinline NoGoods&
    BAB::nogoods(void) {
      return path;
    }
  
    forceinline 
    BAB::~BAB(void) {
      path.reset();
      delete best;
      delete cur;
    }
  
  }}}
  
  #endif
  
  // STATISTICS: search-sequential
  