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 "lib/config.h"
00012 #include "lib/common.h"
00013 #include "lib/io.h"
00014 #include "distance/JensenMetric.h"
00015 #include "features/Features.h"
00016 #include "features/SimpleFeatures.h"
00017 
00018 using namespace shogun;
00019 
00020 CJensenMetric::CJensenMetric() : CSimpleDistance<float64_t>()
00021 {
00022 }
00023 
00024 CJensenMetric::CJensenMetric(CSimpleFeatures<float64_t>* l, CSimpleFeatures<float64_t>* r)
00025 : CSimpleDistance<float64_t>()
00026 {
00027     init(l, r);
00028 }
00029 
00030 CJensenMetric::~CJensenMetric()
00031 {
00032     cleanup();
00033 }
00034 
00035 bool CJensenMetric::init(CFeatures* l, CFeatures* r)
00036 {
00037     return CSimpleDistance<float64_t>::init(l,r);
00038 }
00039 
00040 void CJensenMetric::cleanup()
00041 {
00042 }
00043 
00044 float64_t CJensenMetric::compute(int32_t idx_a, int32_t idx_b)
00045 {
00046     int32_t alen, blen;
00047     bool afree, bfree;
00048 
00049     float64_t* avec=
00050         ((CSimpleFeatures<float64_t>*) lhs)->get_feature_vector(idx_a, alen, afree);
00051     float64_t* bvec=
00052         ((CSimpleFeatures<float64_t>*) rhs)->get_feature_vector(idx_b, blen, bfree);
00053 
00054     ASSERT(alen==blen);
00055 
00056     float64_t absTmp = 0;
00057     float64_t result=0;
00058     {
00059         for (int32_t i=0; i<alen; i++)
00060         {
00061             absTmp=0.5*(avec[i]+bvec[i]);
00062             if (absTmp>0)
00063             {
00064                 if(avec[i]>0)
00065                     result+=avec[i]*log(avec[i]/absTmp);
00066                 if(bvec[i]>0)
00067                     result+=bvec[i]*log(bvec[i]/absTmp);
00068             }
00069         }
00070 
00071     }
00072 
00073     ((CSimpleFeatures<float64_t>*) lhs)->free_feature_vector(avec, idx_a, afree);
00074     ((CSimpleFeatures<float64_t>*) rhs)->free_feature_vector(bvec, idx_b, bfree);
00075 
00076 
00077     return result;
00078 }
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