CosineDistance.cpp

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00001 /*
00002  * This program is free software; you can redistribute it and/or modify
00003  * it under the terms of the GNU General Public License as published by
00004  * the Free Software Foundation; either version 3 of the License, or
00005  * (at your option) any later version.
00006  *
00007  * Written (W) 2008-2009 Christian Gehl
00008  * Copyright (C) 2008-2009 Fraunhofer Institute FIRST
00009  */
00010 
00011 #include <shogun/lib/config.h>
00012 #include <shogun/lib/common.h>
00013 #include <shogun/io/SGIO.h>
00014 #include <shogun/distance/CosineDistance.h>
00015 #include <shogun/features/Features.h>
00016 #include <shogun/features/SimpleFeatures.h>
00017 
00018 using namespace shogun;
00019 
00020 CCosineDistance::CCosineDistance()
00021 : CSimpleDistance<float64_t>()
00022 {
00023 }
00024 
00025 CCosineDistance::CCosineDistance(CSimpleFeatures<float64_t>* l, CSimpleFeatures<float64_t>* r)
00026 : CSimpleDistance<float64_t>()
00027 {
00028     init(l, r);
00029 }
00030 
00031 CCosineDistance::~CCosineDistance()
00032 {
00033     cleanup();
00034 }
00035 
00036 bool CCosineDistance::init(CFeatures* l, CFeatures* r)
00037 {
00038     return CSimpleDistance<float64_t>::init(l,r);
00039 }
00040 
00041 void CCosineDistance::cleanup()
00042 {
00043 }
00044 
00045 float64_t CCosineDistance::compute(int32_t idx_a, int32_t idx_b)
00046 {
00047     int32_t alen, blen;
00048     bool afree, bfree;
00049 
00050     float64_t* avec=
00051         ((CSimpleFeatures<float64_t>*) lhs)->get_feature_vector(idx_a, alen, afree);
00052     float64_t* bvec=
00053         ((CSimpleFeatures<float64_t>*) rhs)->get_feature_vector(idx_b, blen, bfree);
00054 
00055     ASSERT(alen==blen);
00056     float64_t s=0;
00057     float64_t ab=0;
00058     float64_t sa=0;
00059     float64_t sb=0;
00060     {
00061         for (int32_t i=0; i<alen; i++)
00062         {
00063             ab+=avec[i]*bvec[i];
00064             sa+=pow(fabs(avec[i]),2);
00065             sb+=pow(fabs(bvec[i]),2);
00066         }
00067     }
00068 
00069     ((CSimpleFeatures<float64_t>*) lhs)->free_feature_vector(avec, idx_a, afree);
00070     ((CSimpleFeatures<float64_t>*) rhs)->free_feature_vector(bvec, idx_b, bfree);
00071     
00072     s=sqrt(sa)*sqrt(sb);
00073     
00074     // trap division by zero
00075     if(s==0)
00076         return 0;
00077 
00078     s=1-ab/s;
00079     if(s<0)
00080         return 0;
00081     else
00082         return s ;
00083 }
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