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<?php
/**
* Zend Framework (http://framework.zend.com/)
*
* @link http://github.com/zendframework/zf2 for the canonical source repository
* @copyright Copyright (c) 2005-2012 Zend Technologies USA Inc. (http://www.zend.com)
* @license http://framework.zend.com/license/new-bsd New BSD License
* @package Zend_Search
*/
namespace ZendSearch\Lucene\Search\Similarity;
use ZendSearch\Lucene\Search\Similarity\AbstractSimilarity;
/**
* @category Zend
* @package Zend_Search_Lucene
* @subpackage Search
*/
class DefaultSimilarity extends AbstractSimilarity
{
/**
* Implemented as '1/sqrt(numTerms)'.
*
* @param string $fieldName
* @param integer $numTerms
* @return float
*/
public function lengthNorm($fieldName, $numTerms)
{
if ($numTerms == 0) {
return 1E10;
}
return 1.0/sqrt($numTerms);
}
/**
* Implemented as '1/sqrt(sumOfSquaredWeights)'.
*
* @param float $sumOfSquaredWeights
* @return float
*/
public function queryNorm($sumOfSquaredWeights)
{
return 1.0/sqrt($sumOfSquaredWeights);
}
/**
* Implemented as 'sqrt(freq)'.
*
* @param float $freq
* @return float
*/
public function tf($freq)
{
return sqrt($freq);
}
/**
* Implemented as '1/(distance + 1)'.
*
* @param integer $distance
* @return float
*/
public function sloppyFreq($distance)
{
return 1.0/($distance + 1);
}
/**
* Implemented as 'log(numDocs/(docFreq+1)) + 1'.
*
* @param integer $docFreq
* @param integer $numDocs
* @return float
*/
public function idfFreq($docFreq, $numDocs)
{
return log($numDocs/(float)($docFreq+1)) + 1.0;
}
/**
* Implemented as 'overlap/maxOverlap'.
*
* @param integer $overlap
* @param integer $maxOverlap
* @return float
*/
public function coord($overlap, $maxOverlap)
{
return $overlap/(float)$maxOverlap;
}
}