xapian-core  1.4.21
tradeweight.cc
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1 
4 /* Copyright (C) 2013 Aarsh Shah
5  *
6  * This program is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU General Public License as
8  * published by the Free Software Foundation; either version 2 of the
9  * License, or (at your option) any later version.
10  *
11  * This program is distributed in the hope that it will be useful
12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14  * GNU General Public License for more details.
15  *
16  * You should have received a copy of the GNU General Public License
17  * along with this program; if not, write to the Free Software
18  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
19  */
20 
21 #include <config.h>
22 
23 #include "expandweight.h"
24 #include <cmath>
25 
26 using namespace std;
27 
28 namespace Xapian {
29 namespace Internal {
30 
31 double
32 TradEWeight::get_weight() const
33 {
34  double reldocs_without_term = get_rsize() - stats.rtermfreq;
35  double num, denom;
36  num = (stats.rtermfreq + 0.5) * (get_dbsize() - stats.termfreq - reldocs_without_term + 0.5);
37 
38  denom = (stats.termfreq - stats.rtermfreq + 0.5) * (reldocs_without_term + 0.5);
39 
40  double tw = log(num / denom);
41  return stats.multiplier * tw;
42 }
43 
44 }
45 }
The Xapian namespace contains public interfaces for the Xapian library.
Definition: compactor.cc:80
STL namespace.
Collate statistics and calculate the term weights for the ESet.