// $Id$ /*********************************************************************** 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_HypothesisStackNormal_h #define moses_HypothesisStackNormal_h #include #include #include "Hypothesis.h" #include "HypothesisStack.h" #include "WordsBitmap.h" namespace Moses { // class WordsBitmap; // typedef size_t WordsBitmapID; /** A stack for standard phrase-based decoding. */ class HypothesisStackNormal: public HypothesisStack { public: friend std::ostream& operator<<(std::ostream&, const HypothesisStackNormal&); protected: float m_bestScore; /**< score of the best hypothesis in collection */ float m_worstScore; /**< score of the worse hypothesis in collection */ std::map< WordsBitmapID, float > m_diversityWorstScore; /**< score of worst hypothesis for particular source word coverage */ float m_beamWidth; /**< minimum score due to threashold pruning */ size_t m_maxHypoStackSize; /**< maximum number of hypothesis allowed in this stack */ size_t m_minHypoStackDiversity; /**< minimum number of hypothesis with different source word coverage */ 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 Add(Hypothesis *hypothesis); /** destroy all instances of Hypothesis in this collection */ void RemoveAll(); void SetWorstScoreForBitmap( WordsBitmapID id, float worstScore ) { m_diversityWorstScore[ id ] = worstScore; } public: float GetWorstScoreForBitmap( WordsBitmapID id ) { if (m_diversityWorstScore.find( id ) == m_diversityWorstScore.end()) return -std::numeric_limits::infinity(); return m_diversityWorstScore[ id ]; } virtual float GetWorstScoreForBitmap( const WordsBitmap &coverage ) { return GetWorstScoreForBitmap( coverage.GetID() ); } HypothesisStackNormal(Manager& manager); /** 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); /** set maximum number of hypotheses in the collection * \param maxHypoStackSize maximum number (typical number: 100) * \param maxHypoStackSize maximum number (defauly: 0) */ inline void SetMaxHypoStackSize(size_t maxHypoStackSize, size_t minHypoStackDiversity) { m_maxHypoStackSize = maxHypoStackSize; m_minHypoStackDiversity = minHypoStackDiversity; } /** 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 allowable score */ inline float GetWorstScore() const { return m_worstScore; } /** 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 GetSortedList() const; std::vector GetSortedListNOTCONST(); /** 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