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OneStepMarkovChain.hpp

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00001 /*==========================================================================
00002  * Copyright (c) 2001 Carnegie Mellon University.  All Rights Reserved.
00003  *
00004  * Use of the Lemur Toolkit for Language Modeling and Information Retrieval
00005  * is subject to the terms of the software license set forth in the LICENSE
00006  * file included with this software, and also available at
00007  * http://www.lemurproject.org/license.html
00008  *
00009  *==========================================================================
00010  */
00011 
00012 
00013 #ifndef _ONESTEPMARKOVCHAIN_HPP
00014 #define _ONESTEPMARKOVCHAIN_HPP
00015 
00016 
00017 #include "Index.hpp"
00018 #include "WeightedIDSet.hpp"
00019 namespace lemur 
00020 {
00021   namespace langmod
00022   {
00023     
00025 
00029     class OneStepMarkovChain {
00030     public:
00032       OneStepMarkovChain(const lemur::utility::WeightedIDSet &docSet, const lemur::api::Index &homeIndex, double *wdNorm, double stopProbAlpha);
00033       ~OneStepMarkovChain();
00034   
00036 
00042 
00043       void startFromWordIteration(lemur::api::TERMID_T toWord) const;
00044       bool hasMoreFromWord() const { 
00045         while (itPos <= ind.termCountUnique() && fromWordPr[itPos]==0) 
00046           itPos++;
00047         return (itPos<= ind.termCountUnique());
00048       }
00050       void nextFromWordProb(lemur::api::TERMID_T &fromWord, double &prob) const ;
00052 
00053     private:
00054       void computeFromWordProb(lemur::api::TERMID_T toWord) const;
00055       const lemur::api::Index &ind;
00056       double alpha;
00057       int *dSet;
00058       double *norm;
00059       mutable double *fromWordPr;
00060       mutable lemur::api::TERMID_T itPos;
00061       mutable lemur::api::TERMID_T curToWord;
00062     };
00063   }
00064 }
00065 
00066 
00067 #endif /* _ONESTEPMARKOVCHAIN_HPP */

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