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GeodesicMetric.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) 2006-2009 Christian Gehl
8  * Copyright (C) 2006-2009 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 
20 {
21 }
22 
25 {
26  init(l, r);
27 }
28 
30 {
31  cleanup();
32 }
33 
34 bool CGeodesicMetric::init(CFeatures* l, CFeatures* r)
35 {
36  bool result=CDenseDistance<float64_t>::init(l,r);
37 
38  return result;
39 }
40 
42 {
43 }
44 
45 float64_t CGeodesicMetric::compute(int32_t idx_a, int32_t idx_b)
46 {
47  int32_t alen, blen;
48  bool afree, bfree;
49 
50  float64_t* avec=
51  ((CDenseFeatures<float64_t>*) lhs)->get_feature_vector(idx_a, alen, afree);
52  float64_t* bvec=
53  ((CDenseFeatures<float64_t>*) rhs)->get_feature_vector(idx_b, blen, bfree);
54 
55  ASSERT(alen==blen)
56 
57  float64_t s=0;
58  float64_t d=0;
59  float64_t nx=0;
60  float64_t ny=0;
61  {
62  for (int32_t i=0; i<alen; i++)
63  {
64  d+=avec[i]*bvec[i];
65  nx+=avec[i]*avec[i];
66  ny+=bvec[i]*bvec[i];
67  s+=avec[i]+bvec[i];
68  }
69  }
70 
71  ((CDenseFeatures<float64_t>*) lhs)->free_feature_vector(avec, idx_a, afree);
72  ((CDenseFeatures<float64_t>*) rhs)->free_feature_vector(bvec, idx_b, bfree);
73 
74 
75  // trap division by zero
76  if(s==0 || nx==0 || ny==0)
77  return 0;
78 
79  d/=CMath::sqrt(nx*ny);
80 
81  // can only happen due to numerical problems
82  if (CMath::abs(d)>1.0)
83  d=CMath::sign(d);
84 
85  return acos(d);
86 }

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