classxapian_1_1tradweight.tex

xapian 是一个“Xapian 是一个开源概率论信息检索库

\hypertarget{classXapian_1_1TradWeight}{
\section{Xapian::Trad\-Weight Class Reference}
\label{classXapian_1_1TradWeight}\index{Xapian::TradWeight@{Xapian::TradWeight}}
}
Traditional probabilistic weighting scheme (as used by Muscat 3.6).  


{\tt \#include $<$enquire.h$>$}

Inheritance diagram for Xapian::Trad\-Weight:\begin{figure}[H]
\begin{center}
\leavevmode
\includegraphics[width=72pt]{classXapian_1_1TradWeight__inherit__graph}
\end{center}
\end{figure}
Collaboration diagram for Xapian::Trad\-Weight:\begin{figure}[H]
\begin{center}
\leavevmode
\includegraphics[width=72pt]{classXapian_1_1TradWeight__coll__graph}
\end{center}
\end{figure}
\subsection*{Public Member Functions}
\begin{CompactItemize}
\item 
\hyperlink{classXapian_1_1TradWeight_2f41ca5532ba3ed2c1112d792dc5c2db}{Trad\-Weight} (double k)
\begin{CompactList}\small\item\em Construct a \hyperlink{classXapian_1_1TradWeight}{Trad\-Weight}. \item\end{CompactList}\item 
\hyperlink{classXapian_1_1TradWeight}{Trad\-Weight} $\ast$ \hyperlink{classXapian_1_1TradWeight_85727fdd8a794534c5ec2b6da6baf135}{clone} () const 
\begin{CompactList}\small\item\em Return a new weight object of this type. \item\end{CompactList}\item 
std::string \hyperlink{classXapian_1_1TradWeight_a34538148bb8a2771675117d7331aee1}{name} () const 
\begin{CompactList}\small\item\em Name of the weighting scheme. \item\end{CompactList}\item 
std::string \hyperlink{classXapian_1_1TradWeight_3cb90ec9c8ef2866dfa405d3490d4cc3}{serialise} () const 
\begin{CompactList}\small\item\em Serialise object parameters into a string. \item\end{CompactList}\item 
\hyperlink{classXapian_1_1TradWeight}{Trad\-Weight} $\ast$ \hyperlink{classXapian_1_1TradWeight_ce5aae016fc57407c7f7f5f0f3d7b5c0}{unserialise} (const std::string \&s) const 
\begin{CompactList}\small\item\em Create object given string serialisation returned by \hyperlink{classXapian_1_1TradWeight_3cb90ec9c8ef2866dfa405d3490d4cc3}{serialise()}. \item\end{CompactList}\item 
\hyperlink{types_8h_167860ee249b702eb746dca0d245f808}{Xapian::weight} \hyperlink{classXapian_1_1TradWeight_baf2e363758436ec0df6be1120196cfe}{get\_\-sumpart} (\hyperlink{types_8h_6979d98ebbe67186bd31e5ee2a7585cb}{Xapian::termcount} wdf, \hyperlink{types_8h_7272583216038f810105df7dc927723c}{Xapian::doclength} len) const 
\begin{CompactList}\small\item\em Get a weight which is part of the sum over terms being performed. \item\end{CompactList}\item 
\hyperlink{types_8h_167860ee249b702eb746dca0d245f808}{Xapian::weight} \hyperlink{classXapian_1_1TradWeight_bc2fd38d6abbb7ef77b14959ae3f1fc0}{get\_\-maxpart} () const 
\begin{CompactList}\small\item\em Gets the maximum value that \hyperlink{classXapian_1_1TradWeight_baf2e363758436ec0df6be1120196cfe}{get\_\-sumpart()} may return. \item\end{CompactList}\item 
\hyperlink{types_8h_167860ee249b702eb746dca0d245f808}{Xapian::weight} \hyperlink{classXapian_1_1TradWeight_6602159c73f926a5c717af04d53b4c18}{get\_\-sumextra} (\hyperlink{types_8h_7272583216038f810105df7dc927723c}{Xapian::doclength} len) const 
\begin{CompactList}\small\item\em Get an extra weight for a document to add to the sum calculated over the query terms. \item\end{CompactList}\item 
\hyperlink{types_8h_167860ee249b702eb746dca0d245f808}{Xapian::weight} \hyperlink{classXapian_1_1TradWeight_5e06ecfe3f4ad59c4e1a651f604800e2}{get\_\-maxextra} () const 
\begin{CompactList}\small\item\em Gets the maximum value that \hyperlink{classXapian_1_1TradWeight_6602159c73f926a5c717af04d53b4c18}{get\_\-sumextra()} may return. \item\end{CompactList}\item 
bool \hyperlink{classXapian_1_1TradWeight_183bfaab8cf24df3f43982c447b62f7a}{get\_\-sumpart\_\-needs\_\-doclength} () const 
\begin{CompactList}\small\item\em return false if the weight object doesn't need doclength \item\end{CompactList}\end{CompactItemize}


\subsection{Detailed Description}
Traditional probabilistic weighting scheme (as used by Muscat 3.6). 

The Traditional weighting scheme formula is \[ \sum_{t}\frac{f_{t,d}}{k.L_{d}+f_{t,d}}.w_{t} \] where\begin{itemize}
\item $w_{t}$ is the termweight of term t\item $f_{t,d}$ is the within document frequency of term t in document d\item $L_{d}$ is the normalised length of document d\item $k$ is a user specifiable parameter\end{itemize}


Trad\-Weight(k) is equivalent to BM25Weight(k, 0, 0, 1, 0), except that the latter returns weights (k+1) times larger. 



\subsection{Constructor \& Destructor Documentation}
\hypertarget{classXapian_1_1TradWeight_2f41ca5532ba3ed2c1112d792dc5c2db}{
\index{Xapian::TradWeight@{Xapian::Trad\-Weight}!TradWeight@{TradWeight}}
\index{TradWeight@{TradWeight}!Xapian::TradWeight@{Xapian::Trad\-Weight}}
\subsubsection[TradWeight]{\setlength{\rightskip}{0pt plus 5cm}Xapian::Trad\-Weight::Trad\-Weight (double {\em k})\hspace{0.3cm}{\tt  \mbox{[}inline, explicit\mbox{]}}}}
\label{classXapian_1_1TradWeight_2f41ca5532ba3ed2c1112d792dc5c2db}


Construct a \hyperlink{classXapian_1_1TradWeight}{Trad\-Weight}. 

\begin{Desc}
\item[Parameters:]
\begin{description}
\item[{\em k}]parameter governing the importance of within document frequency and document length - any non-negative number (0 meaning to ignore wdf and doc length when calculating weights). Default is 1. \end{description}
\end{Desc}


\subsection{Member Function Documentation}
\hypertarget{classXapian_1_1TradWeight_85727fdd8a794534c5ec2b6da6baf135}{
\index{Xapian::TradWeight@{Xapian::Trad\-Weight}!clone@{clone}}
\index{clone@{clone}!Xapian::TradWeight@{Xapian::Trad\-Weight}}
\subsubsection[clone]{\setlength{\rightskip}{0pt plus 5cm}\hyperlink{classXapian_1_1TradWeight}{Trad\-Weight}$\ast$ Xapian::Trad\-Weight::clone () const\hspace{0.3cm}{\tt  \mbox{[}virtual\mbox{]}}}}
\label{classXapian_1_1TradWeight_85727fdd8a794534c5ec2b6da6baf135}


Return a new weight object of this type. 

A subclass called Foo\-Weight taking parameters param1 and param2 should implement this as:

virtual Foo\-Weight $\ast$ \hyperlink{classXapian_1_1TradWeight_85727fdd8a794534c5ec2b6da6baf135}{clone() const} \{ return new Foo\-Weight(param1, param2); \} 

Implements \hyperlink{classXapian_1_1Weight}{Xapian::Weight}.\hypertarget{classXapian_1_1TradWeight_5e06ecfe3f4ad59c4e1a651f604800e2}{
\index{Xapian::TradWeight@{Xapian::Trad\-Weight}!get_maxextra@{get\_\-maxextra}}
\index{get_maxextra@{get\_\-maxextra}!Xapian::TradWeight@{Xapian::Trad\-Weight}}
\subsubsection[get\_\-maxextra]{\setlength{\rightskip}{0pt plus 5cm}\hyperlink{types_8h_167860ee249b702eb746dca0d245f808}{Xapian::weight} Xapian::Trad\-Weight::get\_\-maxextra () const\hspace{0.3cm}{\tt  \mbox{[}virtual\mbox{]}}}}
\label{classXapian_1_1TradWeight_5e06ecfe3f4ad59c4e1a651f604800e2}


Gets the maximum value that \hyperlink{classXapian_1_1TradWeight_6602159c73f926a5c717af04d53b4c18}{get\_\-sumextra()} may return. 

This is used in optimising searches. 

Implements \hyperlink{classXapian_1_1Weight_ca641ecc2f5645666820f864d243f46d}{Xapian::Weight}.\hypertarget{classXapian_1_1TradWeight_bc2fd38d6abbb7ef77b14959ae3f1fc0}{
\index{Xapian::TradWeight@{Xapian::Trad\-Weight}!get_maxpart@{get\_\-maxpart}}
\index{get_maxpart@{get\_\-maxpart}!Xapian::TradWeight@{Xapian::Trad\-Weight}}
\subsubsection[get\_\-maxpart]{\setlength{\rightskip}{0pt plus 5cm}\hyperlink{types_8h_167860ee249b702eb746dca0d245f808}{Xapian::weight} Xapian::Trad\-Weight::get\_\-maxpart () const\hspace{0.3cm}{\tt  \mbox{[}virtual\mbox{]}}}}
\label{classXapian_1_1TradWeight_bc2fd38d6abbb7ef77b14959ae3f1fc0}


Gets the maximum value that \hyperlink{classXapian_1_1TradWeight_baf2e363758436ec0df6be1120196cfe}{get\_\-sumpart()} may return. 

This is used in optimising searches, by having the postlist tree decay appropriately when parts of it can have limited, or no, further effect. 

Implements \hyperlink{classXapian_1_1Weight_f37e797fa12bb915f73b20b953a132b7}{Xapian::Weight}.\hypertarget{classXapian_1_1TradWeight_6602159c73f926a5c717af04d53b4c18}{
\index{Xapian::TradWeight@{Xapian::Trad\-Weight}!get_sumextra@{get\_\-sumextra}}
\index{get_sumextra@{get\_\-sumextra}!Xapian::TradWeight@{Xapian::Trad\-Weight}}
\subsubsection[get\_\-sumextra]{\setlength{\rightskip}{0pt plus 5cm}\hyperlink{types_8h_167860ee249b702eb746dca0d245f808}{Xapian::weight} Xapian::Trad\-Weight::get\_\-sumextra (\hyperlink{types_8h_7272583216038f810105df7dc927723c}{Xapian::doclength} {\em len}) const\hspace{0.3cm}{\tt  \mbox{[}virtual\mbox{]}}}}
\label{classXapian_1_1TradWeight_6602159c73f926a5c717af04d53b4c18}


Get an extra weight for a document to add to the sum calculated over the query terms. 

This returns a weight for a given document, and is used by some weighting schemes to account for influence such as document length.

\begin{Desc}
\item[Parameters:]
\begin{description}
\item[{\em len}]the (unnormalised) document length. \end{description}
\end{Desc}


Implements \hyperlink{classXapian_1_1Weight_5b39302405b8d10911b26d796ba3f430}{Xapian::Weight}.\hypertarget{classXapian_1_1TradWeight_baf2e363758436ec0df6be1120196cfe}{
\index{Xapian::TradWeight@{Xapian::Trad\-Weight}!get_sumpart@{get\_\-sumpart}}
\index{get_sumpart@{get\_\-sumpart}!Xapian::TradWeight@{Xapian::Trad\-Weight}}
\subsubsection[get\_\-sumpart]{\setlength{\rightskip}{0pt plus 5cm}\hyperlink{types_8h_167860ee249b702eb746dca0d245f808}{Xapian::weight} Xapian::Trad\-Weight::get\_\-sumpart (\hyperlink{types_8h_6979d98ebbe67186bd31e5ee2a7585cb}{Xapian::termcount} {\em wdf}, \hyperlink{types_8h_7272583216038f810105df7dc927723c}{Xapian::doclength} {\em len}) const\hspace{0.3cm}{\tt  \mbox{[}virtual\mbox{]}}}}
\label{classXapian_1_1TradWeight_baf2e363758436ec0df6be1120196cfe}


Get a weight which is part of the sum over terms being performed. 

This returns a weight for a given term and document. These weights are summed to give a total weight for the document.

\begin{Desc}
\item[Parameters:]
\begin{description}
\item[{\em wdf}]the within document frequency of the term. \item[{\em len}]the (unnormalised) document length. \end{description}
\end{Desc}


Implements \hyperlink{classXapian_1_1Weight_cf94e6ef70e95adf04c70fee3f3c965b}{Xapian::Weight}.\hypertarget{classXapian_1_1TradWeight_183bfaab8cf24df3f43982c447b62f7a}{
\index{Xapian::TradWeight@{Xapian::Trad\-Weight}!get_sumpart_needs_doclength@{get\_\-sumpart\_\-needs\_\-doclength}}
\index{get_sumpart_needs_doclength@{get\_\-sumpart\_\-needs\_\-doclength}!Xapian::TradWeight@{Xapian::Trad\-Weight}}
\subsubsection[get\_\-sumpart\_\-needs\_\-doclength]{\setlength{\rightskip}{0pt plus 5cm}bool Xapian::Trad\-Weight::get\_\-sumpart\_\-needs\_\-doclength () const\hspace{0.3cm}{\tt  \mbox{[}virtual\mbox{]}}}}
\label{classXapian_1_1TradWeight_183bfaab8cf24df3f43982c447b62f7a}


return false if the weight object doesn't need doclength 



Reimplemented from \hyperlink{classXapian_1_1Weight_11a52ff08a2277bb765d579bf0ab77d8}{Xapian::Weight}.\hypertarget{classXapian_1_1TradWeight_a34538148bb8a2771675117d7331aee1}{
\index{Xapian::TradWeight@{Xapian::Trad\-Weight}!name@{name}}
\index{name@{name}!Xapian::TradWeight@{Xapian::Trad\-Weight}}
\subsubsection[name]{\setlength{\rightskip}{0pt plus 5cm}std::string Xapian::Trad\-Weight::name () const\hspace{0.3cm}{\tt  \mbox{[}virtual\mbox{]}}}}
\label{classXapian_1_1TradWeight_a34538148bb8a2771675117d7331aee1}


Name of the weighting scheme. 

If the subclass is called Foo\-Weight, this should return \char`\"{}Foo\char`\"{}. 

Implements \hyperlink{classXapian_1_1Weight_10f2a94ec786e68633012c41ecedc123}{Xapian::Weight}.\hypertarget{classXapian_1_1TradWeight_3cb90ec9c8ef2866dfa405d3490d4cc3}{
\index{Xapian::TradWeight@{Xapian::Trad\-Weight}!serialise@{serialise}}
\index{serialise@{serialise}!Xapian::TradWeight@{Xapian::Trad\-Weight}}
\subsubsection[serialise]{\setlength{\rightskip}{0pt plus 5cm}std::string Xapian::Trad\-Weight::serialise () const\hspace{0.3cm}{\tt  \mbox{[}virtual\mbox{]}}}}
\label{classXapian_1_1TradWeight_3cb90ec9c8ef2866dfa405d3490d4cc3}


Serialise object parameters into a string. 



Implements \hyperlink{classXapian_1_1Weight_a395a7cb4abd4ae0a3acc8b7d2510620}{Xapian::Weight}.\hypertarget{classXapian_1_1TradWeight_ce5aae016fc57407c7f7f5f0f3d7b5c0}{
\index{Xapian::TradWeight@{Xapian::Trad\-Weight}!unserialise@{unserialise}}
\index{unserialise@{unserialise}!Xapian::TradWeight@{Xapian::Trad\-Weight}}
\subsubsection[unserialise]{\setlength{\rightskip}{0pt plus 5cm}\hyperlink{classXapian_1_1TradWeight}{Trad\-Weight}$\ast$ Xapian::Trad\-Weight::unserialise (const std::string \& {\em s}) const\hspace{0.3cm}{\tt  \mbox{[}virtual\mbox{]}}}}
\label{classXapian_1_1TradWeight_ce5aae016fc57407c7f7f5f0f3d7b5c0}


Create object given string serialisation returned by \hyperlink{classXapian_1_1TradWeight_3cb90ec9c8ef2866dfa405d3490d4cc3}{serialise()}. 



Implements \hyperlink{classXapian_1_1Weight_c7406de40d11ffa4ef044d641a458484}{Xapian::Weight}.

The documentation for this class was generated from the following file:\begin{CompactItemize}
\item 
include/xapian/\hyperlink{enquire_8h}{enquire.h}\end{CompactItemize}