SHOGUN
v2.0.0
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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) 2012 Viktor Gal 00008 * Copyright (C) 2012 Viktor Gal 00009 */ 00010 00011 #include <shogun/lib/common.h> 00012 #include <shogun/kernel/JensenShannonKernel.h> 00013 #include <shogun/features/Features.h> 00014 #include <shogun/io/SGIO.h> 00015 00016 using namespace shogun; 00017 00018 CJensenShannonKernel::CJensenShannonKernel() 00019 : CDotKernel(0) 00020 { 00021 } 00022 00023 CJensenShannonKernel::CJensenShannonKernel(int32_t size) 00024 : CDotKernel(size) 00025 { 00026 } 00027 00028 CJensenShannonKernel::CJensenShannonKernel( 00029 CDenseFeatures<float64_t>* l, CDenseFeatures<float64_t>* r, int32_t size) 00030 : CDotKernel(size) 00031 { 00032 init(l,r); 00033 } 00034 00035 CJensenShannonKernel::~CJensenShannonKernel() 00036 { 00037 cleanup(); 00038 } 00039 00040 bool CJensenShannonKernel::init(CFeatures* l, CFeatures* r) 00041 { 00042 bool result=CDotKernel::init(l,r); 00043 init_normalizer(); 00044 return result; 00045 } 00046 00047 float64_t CJensenShannonKernel::compute(int32_t idx_a, int32_t idx_b) 00048 { 00049 int32_t alen, blen; 00050 bool afree, bfree; 00051 00052 float64_t* avec= 00053 ((CDenseFeatures<float64_t>*) lhs)->get_feature_vector(idx_a, alen, afree); 00054 float64_t* bvec= 00055 ((CDenseFeatures<float64_t>*) rhs)->get_feature_vector(idx_b, blen, bfree); 00056 ASSERT(alen==blen); 00057 00058 float64_t result=0; 00059 00060 /* calcualte Jensen-Shannon kernel */ 00061 for (int32_t i=0; i<alen; i++) { 00062 float64_t a_i = 0, b_i = 0; 00063 float64_t ab = avec[i]+bvec[i]; 00064 if (avec[i] != 0) 00065 a_i = avec[i] * CMath::log2(ab/avec[i]); 00066 if (bvec[i] != 0) 00067 b_i = bvec[i] * CMath::log2(ab/bvec[i]); 00068 00069 result += 0.5*(a_i + b_i); 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 return result; 00076 } 00077