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CosineDistance.cpp
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1 /*
2  * This program is free software; you can redistribute it and/or modify
3  * it under the terms of the GNU General Public License as published by
4  * the Free Software Foundation; either version 3 of the License, or
5  * (at your option) any later version.
6  *
7  * Written (W) 2008-2009 Christian Gehl
8  * Copyright (C) 2008-2009 Fraunhofer Institute FIRST
9  */
10 
11 #include <shogun/lib/config.h>
12 #include <shogun/lib/common.h>
13 #include <shogun/io/SGIO.h>
16 
17 using namespace shogun;
18 
21 {
22 }
23 
26 {
27  init(l, r);
28 }
29 
31 {
32  cleanup();
33 }
34 
35 bool CCosineDistance::init(CFeatures* l, CFeatures* r)
36 {
38 }
39 
41 {
42 }
43 
44 float64_t CCosineDistance::compute(int32_t idx_a, int32_t idx_b)
45 {
46  int32_t alen, blen;
47  bool afree, bfree;
48 
49  float64_t* avec=
50  ((CDenseFeatures<float64_t>*) lhs)->get_feature_vector(idx_a, alen, afree);
51  float64_t* bvec=
52  ((CDenseFeatures<float64_t>*) rhs)->get_feature_vector(idx_b, blen, bfree);
53 
54  ASSERT(alen==blen)
55  float64_t s=0;
56  float64_t ab=0;
57  float64_t sa=0;
58  float64_t sb=0;
59  {
60  for (int32_t i=0; i<alen; i++)
61  {
62  ab+=avec[i]*bvec[i];
63  sa+=pow(fabs(avec[i]),2);
64  sb+=pow(fabs(bvec[i]),2);
65  }
66  }
67 
68  ((CDenseFeatures<float64_t>*) lhs)->free_feature_vector(avec, idx_a, afree);
69  ((CDenseFeatures<float64_t>*) rhs)->free_feature_vector(bvec, idx_b, bfree);
70 
71  s=sqrt(sa)*sqrt(sb);
72 
73  // trap division by zero
74  if(s==0)
75  return 0;
76 
77  s=1-ab/s;
78  if(s<0)
79  return 0;
80  else
81  return s ;
82 }

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