JensenMetric.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) 2006-2009 Christian Gehl
00008  * Copyright (C) 2006-2009 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/JensenMetric.h>
00015 #include <shogun/features/Features.h>
00016 
00017 using namespace shogun;
00018 
00019 CJensenMetric::CJensenMetric() : CDenseDistance<float64_t>()
00020 {
00021 }
00022 
00023 CJensenMetric::CJensenMetric(CDenseFeatures<float64_t>* l, CDenseFeatures<float64_t>* r)
00024 : CDenseDistance<float64_t>()
00025 {
00026     init(l, r);
00027 }
00028 
00029 CJensenMetric::~CJensenMetric()
00030 {
00031     cleanup();
00032 }
00033 
00034 bool CJensenMetric::init(CFeatures* l, CFeatures* r)
00035 {
00036     return CDenseDistance<float64_t>::init(l,r);
00037 }
00038 
00039 void CJensenMetric::cleanup()
00040 {
00041 }
00042 
00043 float64_t CJensenMetric::compute(int32_t idx_a, int32_t idx_b)
00044 {
00045     int32_t alen, blen;
00046     bool afree, bfree;
00047 
00048     float64_t* avec=
00049         ((CDenseFeatures<float64_t>*) lhs)->get_feature_vector(idx_a, alen, afree);
00050     float64_t* bvec=
00051         ((CDenseFeatures<float64_t>*) rhs)->get_feature_vector(idx_b, blen, bfree);
00052 
00053     ASSERT(alen==blen);
00054 
00055     float64_t absTmp = 0;
00056     float64_t result=0;
00057     {
00058         for (int32_t i=0; i<alen; i++)
00059         {
00060             absTmp=0.5*(avec[i]+bvec[i]);
00061             if (absTmp>0)
00062             {
00063                 if(avec[i]>0)
00064                     result+=avec[i]*log(avec[i]/absTmp);
00065                 if(bvec[i]>0)
00066                     result+=bvec[i]*log(bvec[i]/absTmp);
00067             }
00068         }
00069 
00070     }
00071 
00072     ((CDenseFeatures<float64_t>*) lhs)->free_feature_vector(avec, idx_a, afree);
00073     ((CDenseFeatures<float64_t>*) rhs)->free_feature_vector(bvec, idx_b, bfree);
00074 
00075 
00076     return result;
00077 }
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