trellispath.h.svn-base

moses开源的机器翻译系统

// $Id$

/***********************************************************************
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
***********************************************************************/

#pragma once

#include <iostream>
#include <vector>
#include <limits>
#include "Hypothesis.h"
#include "TypeDef.h"

class TrellisPathCollection;

/** Encapsulate the set of hypotheses/arcs that goes from decoding 1 phrase to all the source phrases
 *	to reach a final translation. For the best translation, this consist of all hypotheses, for the other 
 *	n-best paths, the node on the path can consist of hypotheses or arcs
 */
class TrellisPath
{
	friend std::ostream& operator<<(std::ostream&, const TrellisPath&);

protected:
	std::vector<const Hypothesis *> m_path; //< list of hypotheses/arcs
	size_t		m_prevEdgeChanged; /**< the last node that was wiggled to create this path
																	, or NOT_FOUND if this path is the best trans so consist of only hypos
															 */

	ScoreComponentCollection	m_scoreBreakdown;
	float m_totalScore;

public:
	TrellisPath(); // not implemented
	
	//! create path OF pure hypo
	TrellisPath(const Hypothesis *hypo);
		
	/** create path from another path, deviate at edgeIndex by using arc instead, 
		* which may change other hypo back from there
		*/
	TrellisPath(const TrellisPath &copy, size_t edgeIndex, const Hypothesis *arc);
	
	inline float GetTotalScore() const { return m_totalScore; }

	/** list of each hypo/arcs in path. For anything other than the best hypo, it is not possible just to follow the
		* m_prevHypo variable in the hypothesis object
		*/
	inline const std::vector<const Hypothesis *> &GetEdges() const
	{
		return m_path;
	}
	
	//! create a set of next best paths by wiggling 1 of the node at a time. 
	void CreateDeviantPaths(TrellisPathCollection &pathColl) const;

	inline const ScoreComponentCollection &GetScoreBreakdown() const
	{
		return m_scoreBreakdown;
	}
	
	Phrase GetTargetPhrase() const;
	Phrase GetSurfacePhrase() const;
	
	TO_STRING();

};

// friend
inline std::ostream& operator<<(std::ostream& out, const TrellisPath& path)
{
	const size_t sizePath = path.m_path.size();
	for (int pos = (int) sizePath - 1 ; pos >= 0 ; pos--)
	{
		const Hypothesis *edge = path.m_path[pos];
		const WordsRange &sourceRange = edge->GetCurrSourceWordsRange();
		out << edge->GetId() << " " << sourceRange.GetStartPos() << "-" << sourceRange.GetEndPos() << ", ";
	}
	// scores
	out << " total=" << path.GetTotalScore()
			<< " " << path.GetScoreBreakdown()
			<< std::endl;

	return out;
}