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<?php
/**
* Zend Framework
*
* LICENSE
*
* This source file is subject to the new BSD license that is bundled
* with this package in the file LICENSE.txt.
* It is also available through the world-wide-web at this URL:
* http://framework.zend.com/license/new-bsd
* If you did not receive a copy of the license and are unable to
* obtain it through the world-wide-web, please send an email
* to license@zend.com so we can send you a copy immediately.
*
* @category Zend
* @package Zend_Search_Lucene
* @subpackage Search
* @copyright Copyright (c) 2005-2009 Zend Technologies USA Inc. (http://www.zend.com)
* @license http://framework.zend.com/license/new-bsd New BSD License
* @version $Id: Similarity.php 18954 2009-11-12 20:01:33Z alexander $
*/
/**
* @category Zend
* @package Zend_Search_Lucene
* @subpackage Search
* @copyright Copyright (c) 2005-2009 Zend Technologies USA Inc. (http://www.zend.com)
* @license http://framework.zend.com/license/new-bsd New BSD License
*/
abstract class Zend_Search_Lucene_Search_Similarity
{
/**
* The Similarity implementation used by default.
*
* @var Zend_Search_Lucene_Search_Similarity
*/
private static $_defaultImpl;
/**
* Cache of decoded bytes.
* Array of floats
*
* @var array
*/
private static $_normTable = array( 0 => 0.0,
1 => 5.820766E-10,
2 => 6.9849193E-10,
3 => 8.1490725E-10,
4 => 9.313226E-10,
5 => 1.1641532E-9,
6 => 1.3969839E-9,
7 => 1.6298145E-9,
8 => 1.8626451E-9,
9 => 2.3283064E-9,
10 => 2.7939677E-9,
11 => 3.259629E-9,
12 => 3.7252903E-9,
13 => 4.656613E-9,
14 => 5.5879354E-9,
15 => 6.519258E-9,
16 => 7.4505806E-9,
17 => 9.313226E-9,
18 => 1.1175871E-8,
19 => 1.3038516E-8,
20 => 1.4901161E-8,
21 => 1.8626451E-8,
22 => 2.2351742E-8,
23 => 2.6077032E-8,
24 => 2.9802322E-8,
25 => 3.7252903E-8,
26 => 4.4703484E-8,
27 => 5.2154064E-8,
28 => 5.9604645E-8,
29 => 7.4505806E-8,
30 => 8.940697E-8,
31 => 1.0430813E-7,
32 => 1.1920929E-7,
33 => 1.4901161E-7,
34 => 1.7881393E-7,
35 => 2.0861626E-7,
36 => 2.3841858E-7,
37 => 2.9802322E-7,
38 => 3.5762787E-7,
39 => 4.172325E-7,
40 => 4.7683716E-7,
41 => 5.9604645E-7,
42 => 7.1525574E-7,
43 => 8.34465E-7,
44 => 9.536743E-7,
45 => 1.1920929E-6,
46 => 1.4305115E-6,
47 => 1.66893E-6,
48 => 1.9073486E-6,
49 => 2.3841858E-6,
50 => 2.861023E-6,
51 => 3.33786E-6,
52 => 3.8146973E-6,
53 => 4.7683716E-6,
54 => 5.722046E-6,
55 => 6.67572E-6,
56 => 7.6293945E-6,
57 => 9.536743E-6,
58 => 1.1444092E-5,
59 => 1.335144E-5,
60 => 1.5258789E-5,
61 => 1.9073486E-5,
62 => 2.2888184E-5,
63 => 2.670288E-5,
64 => 3.0517578E-5,
65 => 3.8146973E-5,
66 => 4.5776367E-5,
67 => 5.340576E-5,
68 => 6.1035156E-5,
69 => 7.6293945E-5,
70 => 9.1552734E-5,
71 => 1.0681152E-4,
72 => 1.2207031E-4,
73 => 1.5258789E-4,
74 => 1.8310547E-4,
75 => 2.1362305E-4,
76 => 2.4414062E-4,
77 => 3.0517578E-4,
78 => 3.6621094E-4,
79 => 4.272461E-4,
80 => 4.8828125E-4,
81 => 6.1035156E-4,
82 => 7.324219E-4,
83 => 8.544922E-4,
84 => 9.765625E-4,
85 => 0.0012207031,
86 => 0.0014648438,
87 => 0.0017089844,
88 => 0.001953125,
89 => 0.0024414062,
90 => 0.0029296875,
91 => 0.0034179688,
92 => 0.00390625,
93 => 0.0048828125,
94 => 0.005859375,
95 => 0.0068359375,
96 => 0.0078125,
97 => 0.009765625,
98 => 0.01171875,
99 => 0.013671875,
100 => 0.015625,
101 => 0.01953125,
102 => 0.0234375,
103 => 0.02734375,
104 => 0.03125,
105 => 0.0390625,
106 => 0.046875,
107 => 0.0546875,
108 => 0.0625,
109 => 0.078125,
110 => 0.09375,
111 => 0.109375,
112 => 0.125,
113 => 0.15625,
114 => 0.1875,
115 => 0.21875,
116 => 0.25,
117 => 0.3125,
118 => 0.375,
119 => 0.4375,
120 => 0.5,
121 => 0.625,
122 => 0.75,
123 => 0.875,
124 => 1.0,
125 => 1.25,
126 => 1.5,
127 => 1.75,
128 => 2.0,
129 => 2.5,
130 => 3.0,
131 => 3.5,
132 => 4.0,
133 => 5.0,
134 => 6.0,
135 => 7.0,
136 => 8.0,
137 => 10.0,
138 => 12.0,
139 => 14.0,
140 => 16.0,
141 => 20.0,
142 => 24.0,
143 => 28.0,
144 => 32.0,
145 => 40.0,
146 => 48.0,
147 => 56.0,
148 => 64.0,
149 => 80.0,
150 => 96.0,
151 => 112.0,
152 => 128.0,
153 => 160.0,
154 => 192.0,
155 => 224.0,
156 => 256.0,
157 => 320.0,
158 => 384.0,
159 => 448.0,
160 => 512.0,
161 => 640.0,
162 => 768.0,
163 => 896.0,
164 => 1024.0,
165 => 1280.0,
166 => 1536.0,
167 => 1792.0,
168 => 2048.0,
169 => 2560.0,
170 => 3072.0,
171 => 3584.0,
172 => 4096.0,
173 => 5120.0,
174 => 6144.0,
175 => 7168.0,
176 => 8192.0,
177 => 10240.0,
178 => 12288.0,
179 => 14336.0,
180 => 16384.0,
181 => 20480.0,
182 => 24576.0,
183 => 28672.0,
184 => 32768.0,
185 => 40960.0,
186 => 49152.0,
187 => 57344.0,
188 => 65536.0,
189 => 81920.0,
190 => 98304.0,
191 => 114688.0,
192 => 131072.0,
193 => 163840.0,
194 => 196608.0,
195 => 229376.0,
196 => 262144.0,
197 => 327680.0,
198 => 393216.0,
199 => 458752.0,
200 => 524288.0,
201 => 655360.0,
202 => 786432.0,
203 => 917504.0,
204 => 1048576.0,
205 => 1310720.0,
206 => 1572864.0,
207 => 1835008.0,
208 => 2097152.0,
209 => 2621440.0,
210 => 3145728.0,
211 => 3670016.0,
212 => 4194304.0,
213 => 5242880.0,
214 => 6291456.0,
215 => 7340032.0,
216 => 8388608.0,
217 => 1.048576E7,
218 => 1.2582912E7,
219 => 1.4680064E7,
220 => 1.6777216E7,
221 => 2.097152E7,
222 => 2.5165824E7,
223 => 2.9360128E7,
224 => 3.3554432E7,
225 => 4.194304E7,
226 => 5.0331648E7,
227 => 5.8720256E7,
228 => 6.7108864E7,
229 => 8.388608E7,
230 => 1.00663296E8,
231 => 1.17440512E8,
232 => 1.34217728E8,
233 => 1.6777216E8,
234 => 2.01326592E8,
235 => 2.34881024E8,
236 => 2.68435456E8,
237 => 3.3554432E8,
238 => 4.02653184E8,
239 => 4.69762048E8,
240 => 5.3687091E8,
241 => 6.7108864E8,
242 => 8.0530637E8,
243 => 9.395241E8,
244 => 1.07374182E9,
245 => 1.34217728E9,
246 => 1.61061274E9,
247 => 1.87904819E9,
248 => 2.14748365E9,
249 => 2.68435456E9,
250 => 3.22122547E9,
251 => 3.75809638E9,
252 => 4.2949673E9,
253 => 5.3687091E9,
254 => 6.4424509E9,
255 => 7.5161928E9 );
/**
* Set the default Similarity implementation used by indexing and search
* code.
*
* @param Zend_Search_Lucene_Search_Similarity $similarity
*/
public static function setDefault(Zend_Search_Lucene_Search_Similarity $similarity)
{
self::$_defaultImpl = $similarity;
}
/**
* Return the default Similarity implementation used by indexing and search
* code.
*
* @return Zend_Search_Lucene_Search_Similarity
*/
public static function getDefault()
{
if (!self::$_defaultImpl instanceof Zend_Search_Lucene_Search_Similarity) {
require_once 'Zend/Search/Lucene/Search/Similarity/Default.php';
self::$_defaultImpl = new Zend_Search_Lucene_Search_Similarity_Default();
}
return self::$_defaultImpl;
}
/**
* Computes the normalization value for a field given the total number of
* terms contained in a field. These values, together with field boosts, are
* stored in an index and multipled into scores for hits on each field by the
* search code.
*
* Matches in longer fields are less precise, so implemenations of this
* method usually return smaller values when 'numTokens' is large,
* and larger values when 'numTokens' is small.
*
* That these values are computed under
* IndexWriter::addDocument(Document) and stored then using
* encodeNorm(float). Thus they have limited precision, and documents
* must be re-indexed if this method is altered.
*
* fieldName - name of field
* numTokens - the total number of tokens contained in fields named
* 'fieldName' of 'doc'.
* Returns a normalization factor for hits on this field of this document
*
* @param string $fieldName
* @param integer $numTokens
* @return float
*/
abstract public function lengthNorm($fieldName, $numTokens);
/**
* Computes the normalization value for a query given the sum of the squared
* weights of each of the query terms. This value is then multipled into the
* weight of each query term.
*
* This does not affect ranking, but rather just attempts to make scores
* from different queries comparable.
*
* sumOfSquaredWeights - the sum of the squares of query term weights
* Returns a normalization factor for query weights
*
* @param float $sumOfSquaredWeights
* @return float
*/
abstract public function queryNorm($sumOfSquaredWeights);
/**
* Decodes a normalization factor stored in an index.
*
* @param integer $byte
* @return float
*/
public static function decodeNorm($byte)
{
return self::$_normTable[$byte & 0xFF];
}
/**
* Encodes a normalization factor for storage in an index.
*
* The encoding uses a five-bit exponent and three-bit mantissa, thus
* representing values from around 7x10^9 to 2x10^-9 with about one
* significant decimal digit of accuracy. Zero is also represented.
* Negative numbers are rounded up to zero. Values too large to represent
* are rounded down to the largest representable value. Positive values too
* small to represent are rounded up to the smallest positive representable
* value.
*
* @param float $f
* @return integer
*/
static function encodeNorm($f)
{
return self::_floatToByte($f);
}
/**
* Float to byte conversion
*
* @param integer $b
* @return float
*/
private static function _floatToByte($f)
{
// round negatives up to zero
if ($f <= 0.0) {
return 0;
}
// search for appropriate value
$lowIndex = 0;
$highIndex = 255;
while ($highIndex >= $lowIndex) {
// $mid = ($highIndex - $lowIndex)/2;
$mid = ($highIndex + $lowIndex) >> 1;
$delta = $f - self::$_normTable[$mid];
if ($delta < 0) {
$highIndex = $mid-1;
} elseif ($delta > 0) {
$lowIndex = $mid+1;
} else {
return $mid; // We got it!
}
}
// round to closest value
if ($highIndex != 255 &&
$f - self::$_normTable[$highIndex] > self::$_normTable[$highIndex+1] - $f ) {
return $highIndex + 1;
} else {
return $highIndex;
}
}
/**
* Computes a score factor based on a term or phrase's frequency in a
* document. This value is multiplied by the idf(Term, Searcher)
* factor for each term in the query and these products are then summed to
* form the initial score for a document.
*
* Terms and phrases repeated in a document indicate the topic of the
* document, so implementations of this method usually return larger values
* when 'freq' is large, and smaller values when 'freq'
* is small.
*
* freq - the frequency of a term within a document
* Returns a score factor based on a term's within-document frequency
*
* @param float $freq
* @return float
*/
abstract public function tf($freq);
/**
* Computes the amount of a sloppy phrase match, based on an edit distance.
* This value is summed for each sloppy phrase match in a document to form
* the frequency that is passed to tf(float).
*
* A phrase match with a small edit distance to a document passage more
* closely matches the document, so implementations of this method usually
* return larger values when the edit distance is small and smaller values
* when it is large.
*
* distance - the edit distance of this sloppy phrase match
* Returns the frequency increment for this match
*
* @param integer $distance
* @return float
*/
abstract public function sloppyFreq($distance);
/**
* Computes a score factor for a simple term or a phrase.
*
* The default implementation is:
* return idfFreq(searcher.docFreq(term), searcher.maxDoc());
*
* input - the term in question or array of terms
* reader - reader the document collection being searched
* Returns a score factor for the term
*
* @param mixed $input
* @param Zend_Search_Lucene_Interface $reader
* @return a score factor for the term
*/
public function idf($input, Zend_Search_Lucene_Interface $reader)
{
if (!is_array($input)) {
return $this->idfFreq($reader->docFreq($input), $reader->count());
} else {
$idf = 0.0;
foreach ($input as $term) {
$idf += $this->idfFreq($reader->docFreq($term), $reader->count());
}
return $idf;
}
}
/**
* Computes a score factor based on a term's document frequency (the number
* of documents which contain the term). This value is multiplied by the
* tf(int) factor for each term in the query and these products are
* then summed to form the initial score for a document.
*
* Terms that occur in fewer documents are better indicators of topic, so
* implemenations of this method usually return larger values for rare terms,
* and smaller values for common terms.
*
* docFreq - the number of documents which contain the term
* numDocs - the total number of documents in the collection
* Returns a score factor based on the term's document frequency
*
* @param integer $docFreq
* @param integer $numDocs
* @return float
*/
abstract public function idfFreq($docFreq, $numDocs);
/**
* Computes a score factor based on the fraction of all query terms that a
* document contains. This value is multiplied into scores.
*
* The presence of a large portion of the query terms indicates a better
* match with the query, so implemenations of this method usually return
* larger values when the ratio between these parameters is large and smaller
* values when the ratio between them is small.
*
* overlap - the number of query terms matched in the document
* maxOverlap - the total number of terms in the query
* Returns a score factor based on term overlap with the query
*
* @param integer $overlap
* @param integer $maxOverlap
* @return float
*/
abstract public function coord($overlap, $maxOverlap);
}
|