mosesdecoder/moses/HypothesisStackCubePruning.h

// $Id$

/***********************************************************************
Moses - factored phrase-based language decoder
Copyright (C) 2006 University of Edinburgh

This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
***********************************************************************/

#ifndef moses_HypothesisStackCubePruning_h
#define moses_HypothesisStackCubePruning_h

#include <limits>
#include <map>
#include <set>
#include "Hypothesis.h"
#include "BitmapContainer.h"
#include "HypothesisStack.h"

namespace Moses
{

class BitmapContainer;
class TranslationOptionList;
class Manager;

typedef std::map<WordsBitmap, BitmapContainer*> _BMType;

/** A stack for phrase-based decoding with cube-pruning. */
class HypothesisStackCubePruning : public HypothesisStack
{
public:
  friend std::ostream& operator<<(std::ostream&, const HypothesisStackCubePruning&);

protected:
  _BMType m_bitmapAccessor;

  float m_bestScore; /**< score of the best hypothesis in collection */
  float m_worstScore; /**< score of the worse hypthesis in collection */
  float m_beamWidth; /**< minimum score due to threashold pruning */
  size_t m_maxHypoStackSize; /**< maximum number of hypothesis allowed in this stack */
  bool m_nBestIsEnabled; /**< flag to determine whether to keep track of old arcs */

  /** add hypothesis to stack. Prune if necessary.
   * Returns false if equiv hypo exists in collection, otherwise returns true
   */
  std::pair<HypothesisStackCubePruning::iterator, bool> Add(Hypothesis *hypothesis);

  /** destroy all instances of Hypothesis in this collection */
  void RemoveAll();

public:
  HypothesisStackCubePruning(Manager& manager);
  ~HypothesisStackCubePruning() {
    RemoveAll();
    m_bitmapAccessor.clear();
  }

  /** adds the hypo, but only if within thresholds (beamThr, stackSize).
  *	This function will recombine hypotheses silently!  There is no record
  * (could affect n-best list generation...TODO)
  * Call stack for adding hypothesis is
  		AddPrune()
  			Add()
  				AddNoPrune()
  */
  bool AddPrune(Hypothesis *hypothesis);

  void AddInitial(Hypothesis *hypo);

  /** set maximum number of hypotheses in the collection
   * \param maxHypoStackSize maximum number (typical number: 100)
   */
  inline void SetMaxHypoStackSize(size_t maxHypoStackSize) {
    m_maxHypoStackSize = maxHypoStackSize;
  }

  inline size_t GetMaxHypoStackSize() const {
    return m_maxHypoStackSize;
  }

  /** set beam threshold, hypotheses in the stack must not be worse than
    * this factor times the best score to be allowed in the stack
   * \param beamThreshold minimum factor (typical number: 0.03)
   */
  inline void SetBeamWidth(float beamWidth) {
    m_beamWidth = beamWidth;
  }

  /** return score of the best hypothesis in the stack */
  inline float GetBestScore() const {
    return m_bestScore;
  }

  /** return worst score allowed for the stack */
  inline float GetWorstScore() const {
    return m_worstScore;
  }

  void AddHypothesesToBitmapContainers();

  const _BMType& GetBitmapAccessor() const {
    return m_bitmapAccessor;
  }

  void SetBitmapAccessor(const WordsBitmap &newBitmap
                         , HypothesisStackCubePruning &stack
                         , const WordsRange &range
                         , BitmapContainer &bitmapContainer
                         , const SquareMatrix &futureScore
                         , const TranslationOptionList &transOptList);

  /** pruning, if too large.
   * Pruning algorithm: find a threshold and delete all hypothesis below it.
   * The threshold is chosen so that exactly newSize top items remain on the
   * stack in fact, in situations where some of the hypothesis fell below
   * m_beamWidth, the stack will contain less items.
   * \param newSize maximum size */
  void PruneToSize(size_t newSize);

  //! return the hypothesis with best score. Used to get the translated at end of decoding
  const Hypothesis *GetBestHypothesis() const;
  //! return all hypothesis, sorted by descending score. Used in creation of N best list
  std::vector<const Hypothesis*> GetSortedList() const;

  /** make all arcs in point to the equiv hypothesis that contains them.
  * Ie update doubly linked list be hypo & arcs
  */
  void CleanupArcList();

  TO_STRING();
};

}
#endif