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) 1999-2009 Soeren Sonnenburg 00008 * Copyright (C) 1999-2009 Fraunhofer Institute FIRST and Max-Planck-Society 00009 */ 00010 00011 #include <shogun/lib/common.h> 00012 #include <shogun/kernel/Chi2Kernel.h> 00013 #include <shogun/features/Features.h> 00014 #include <shogun/io/SGIO.h> 00015 00016 using namespace shogun; 00017 00018 void 00019 CChi2Kernel::init() 00020 { 00021 SG_ADD(&width, "width", "Kernel width.", MS_AVAILABLE); 00022 } 00023 00024 CChi2Kernel::CChi2Kernel() 00025 : CDotKernel(0), width(0) 00026 { 00027 init(); 00028 } 00029 00030 CChi2Kernel::CChi2Kernel(int32_t size, float64_t w) 00031 : CDotKernel(size), width(w) 00032 { 00033 init(); 00034 } 00035 00036 CChi2Kernel::CChi2Kernel( 00037 CDenseFeatures<float64_t>* l, CDenseFeatures<float64_t>* r, float64_t w, int32_t size) 00038 : CDotKernel(size), width(w) 00039 { 00040 init(); 00041 init(l,r); 00042 } 00043 00044 CChi2Kernel::~CChi2Kernel() 00045 { 00046 cleanup(); 00047 } 00048 00049 bool CChi2Kernel::init(CFeatures* l, CFeatures* r) 00050 { 00051 bool result=CDotKernel::init(l,r); 00052 init_normalizer(); 00053 return result; 00054 } 00055 00056 float64_t CChi2Kernel::compute(int32_t idx_a, int32_t idx_b) 00057 { 00058 int32_t alen, blen; 00059 bool afree, bfree; 00060 00061 float64_t* avec= 00062 ((CDenseFeatures<float64_t>*) lhs)->get_feature_vector(idx_a, alen, afree); 00063 float64_t* bvec= 00064 ((CDenseFeatures<float64_t>*) rhs)->get_feature_vector(idx_b, blen, bfree); 00065 ASSERT(alen==blen); 00066 00067 float64_t result=0; 00068 for (int32_t i=0; i<alen; i++) 00069 { 00070 float64_t n=avec[i]-bvec[i]; 00071 float64_t d=avec[i]+bvec[i]; 00072 if (d!=0) 00073 result+=n*n/d; 00074 } 00075 00076 result=exp(-result/width); 00077 00078 ((CDenseFeatures<float64_t>*) lhs)->free_feature_vector(avec, idx_a, afree); 00079 ((CDenseFeatures<float64_t>*) rhs)->free_feature_vector(bvec, idx_b, bfree); 00080 00081 return result; 00082 }