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00011 #include "lib/common.h"
00012 #include "lib/io.h"
00013 #include "kernel/GaussianMatchStringKernel.h"
00014 #include "kernel/SqrtDiagKernelNormalizer.h"
00015 #include "features/Features.h"
00016 #include "features/StringFeatures.h"
00017
00018 using namespace shogun;
00019
00020 CGaussianMatchStringKernel::CGaussianMatchStringKernel(int32_t size, float64_t w)
00021 : CStringKernel<char>(size), width(w)
00022 {
00023 set_normalizer(new CSqrtDiagKernelNormalizer());
00024 }
00025
00026 CGaussianMatchStringKernel::CGaussianMatchStringKernel(
00027 CStringFeatures<char>* l, CStringFeatures<char>* r, float64_t w)
00028 : CStringKernel<char>(10), width(w)
00029 {
00030 set_normalizer(new CSqrtDiagKernelNormalizer());
00031 init(l, r);
00032 }
00033
00034 CGaussianMatchStringKernel::~CGaussianMatchStringKernel()
00035 {
00036 cleanup();
00037 }
00038
00039 bool CGaussianMatchStringKernel::init(CFeatures* l, CFeatures* r)
00040 {
00041 CStringKernel<char>::init(l, r);
00042 return init_normalizer();
00043 }
00044
00045 void CGaussianMatchStringKernel::cleanup()
00046 {
00047 CKernel::cleanup();
00048 }
00049
00050 float64_t CGaussianMatchStringKernel::compute(int32_t idx_a, int32_t idx_b)
00051 {
00052 int32_t i, alen, blen ;
00053 bool free_avec, free_bvec;
00054
00055 char* avec = ((CStringFeatures<char>*) lhs)->get_feature_vector(idx_a, alen, free_avec);
00056 char* bvec = ((CStringFeatures<char>*) rhs)->get_feature_vector(idx_b, blen, free_bvec);
00057
00058 float64_t result=0;
00059
00060 ASSERT(alen==blen);
00061
00062 for (i = 0; i<alen; i++)
00063 result+=(avec[i]==bvec[i]) ? 0:4;
00064
00065 result=exp(-result/width);
00066
00067
00068 ((CStringFeatures<char>*) lhs)->free_feature_vector(avec, idx_a, free_avec);
00069 ((CStringFeatures<char>*) rhs)->free_feature_vector(bvec, idx_b, free_bvec);
00070 return result;
00071 }