decoder.h

解码器是基于短语的统计机器翻译系统的核心模块

/*
* Decoder.h  -  Decoder class declaration
*
* Copyright (C) 2006 by Zhongjun He <[e-mail]> 
                        Yajuan Lv <[e-mail]>
Multilingual Interaction Technology and Evaluation Laboratory, ICT, CAS

* Begin       : 04/13/2006
* Last Change : 04/13/2006
*
* This program 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 program 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 General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
*/
#ifndef DECODER_H
#define DECODER_H

#ifndef _WIN32
#include <unistd.h>
#endif

#include <fstream>

#include "Candidate.h"
#include "Hypotheses.h"
#include "LanguageModel.h"
#include "SentPair.h"
#include "TTable.h"
using namespace std;

class Decoder
{
public:

	Decoder();

	~Decoder();

	//Read configure
	void ReadConfigure(const char *conf);

	//Set argument
	void SetArg(int bplimit, int dis, int stack, int nbestlist, int print_nbest, int print_info,
		        const string &tf, const string &rf, const string &nf);

	//Initialize
	void Initialize();

	// Translate a sentence                                                 
	vector<CandTrans> TranslateSent(const string &chinese);

	//Translate file
	void TranslateFile();

	//Read Chinese sentences from file
	void ReadChinese(const char *filename, vector<string> &sents);

	//Change Format
	void ChangeFormatTo863(const char *srcfile, const char *tempfile, const char *resultfile);

	string testfile, resultfile, nbestfile;

	int BP_TABLE_LIMIT;
	int MAX_DISTORTION;
	int HP_STACK_SIZE;
	int NBEST_LIST;
	
	bool IS_PRINT_NBEST;//if print n best or not ;
	bool INFO;//INFO=1 show the search information in logfile;



private:
	
	//search possible translations for a Chinese phrase
	void SearchPhrase(const vector<string> &phrase, TransMap &transoption);

	//Compute the Future Cost
	void ComputeFutureCost(int WordLen, const map<pair<int,int>, TransMap> &TransOption,
		                   map<pair<int,int> ,double> &FutureCost);

	//Beam Search
	void BeamSearch(int WordLen, const map<pair<int,int>,TransMap> &TransOption, 
		            vector<vector<Hypotheses> > &HpStack, map<pair<int,int>,double> &FutureCost);

	//Generate Nbest-list
	void GenerateNbest(vector<vector<Hypotheses> > &HpStack, vector<CandTrans> &CandNbest);
	void Generate1best(vector<vector<Hypotheses> > &HpStack, vector<CandTrans> &CandNbest);

	//Push a hypothesis to HpStack
	bool AddToStack(vector<Hypotheses> &HpStack, Hypotheses &hp);

	//get distortion distance
	int GetDistortionDistance(const vector<int> CoveredWord, const pair<int,int> LastPhraseBeginEnd, 
		                      const pair<int,int> BeginEnd);

	//Change the first letter to its upper case
	void TrueCase(string &s);

    vector<double> lambda;//feature function weight

	TTable bptable;//bilingual phrase translation table
	string bpfile;//bilingual phrase file

	LanguageModel lm;//language model
	string lmfile;//language model file
	int lmngram;//n-gram of Language Model,default is 3-gram

	ofstream logs;//logfile

};
#endif