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00012 #include "lib/common.h"
00013 #include "lib/io.h"
00014 #include "kernel/LocalityImprovedStringKernel.h"
00015 #include "features/StringFeatures.h"
00016
00017 using namespace shogun;
00018
00019 CLocalityImprovedStringKernel::CLocalityImprovedStringKernel(
00020 int32_t size, int32_t l, int32_t id, int32_t od)
00021 : CStringKernel<char>(size), length(l), inner_degree(id), outer_degree(od)
00022 {
00023 SG_INFO( "LIK with parms: l=%d, id=%d, od=%d created!\n", l, id, od);
00024 }
00025
00026 CLocalityImprovedStringKernel::CLocalityImprovedStringKernel(
00027 CStringFeatures<char>* l, CStringFeatures<char>* r, int32_t len,
00028 int32_t id, int32_t od)
00029 : CStringKernel<char>(10), length(len), inner_degree(id), outer_degree(od)
00030 {
00031 SG_INFO( "LIK with parms: l=%d, id=%d, od=%d created!\n", len, id, od);
00032
00033 init(l, r);
00034 }
00035
00036 CLocalityImprovedStringKernel::~CLocalityImprovedStringKernel()
00037 {
00038 cleanup();
00039 }
00040
00041 bool CLocalityImprovedStringKernel::init(CFeatures* l, CFeatures* r)
00042 {
00043 CStringKernel<char>::init(l,r);
00044 return init_normalizer();
00045 }
00046
00047 float64_t CLocalityImprovedStringKernel::compute(int32_t idx_a, int32_t idx_b)
00048 {
00049 int32_t alen, blen;
00050 bool free_avec, free_bvec;
00051
00052 char* avec = ((CStringFeatures<char>*) lhs)->get_feature_vector(idx_a, alen, free_avec);
00053 char* bvec = ((CStringFeatures<char>*) rhs)->get_feature_vector(idx_b, blen, free_bvec);
00054
00055 ASSERT(alen==blen && alen>0);
00056
00057 int32_t i,t;
00058 float64_t* match=new float64_t[alen];
00059
00060
00061 for (i = 0; i<alen; i++)
00062 match[i] = (avec[i] == bvec[i])? 1 : 0;
00063
00064 float64_t outer_sum = 0;
00065
00066 for (t = 0; t<alen-length; t++)
00067 {
00068 float64_t sum = 0;
00069 for (i = 0; i<length && t+i+length+1<alen; i++)
00070 sum += (i+1)*match[t+i]+(length-i)*match[t+i+length+1];
00071
00072 float64_t inner_sum = (sum + (length+1)*match[t+length]) / ((2*length+1)*(length+1));
00073 inner_sum = pow(inner_sum, inner_degree + 1);
00074 outer_sum += inner_sum;
00075 }
00076 delete[] match;
00077
00078 ((CStringFeatures<char>*) lhs)->free_feature_vector(avec, idx_a, free_avec);
00079 ((CStringFeatures<char>*) rhs)->free_feature_vector(bvec, idx_b, free_bvec);
00080 return pow(outer_sum, outer_degree + 1);
00081 }