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00012 #include <shogun/lib/common.h>
00013 #include <shogun/io/SGIO.h>
00014 #include <shogun/kernel/LocalityImprovedStringKernel.h>
00015 #include <shogun/features/StringFeatures.h>
00016
00017 using namespace shogun;
00018
00019 CLocalityImprovedStringKernel::CLocalityImprovedStringKernel()
00020 : CStringKernel<char>(0)
00021 {
00022 init();
00023 }
00024
00025 CLocalityImprovedStringKernel::CLocalityImprovedStringKernel(
00026 int32_t size, int32_t l, int32_t id, int32_t od)
00027 : CStringKernel<char>(size)
00028 {
00029 init();
00030
00031 length=l;
00032 inner_degree=id;
00033 outer_degree=od;
00034
00035 SG_INFO( "LIK with parms: l=%d, id=%d, od=%d created!\n", l, id, od);
00036 }
00037
00038 CLocalityImprovedStringKernel::CLocalityImprovedStringKernel(
00039 CStringFeatures<char>* l, CStringFeatures<char>* r, int32_t len,
00040 int32_t id, int32_t od)
00041 : CStringKernel<char>(10)
00042 {
00043 init();
00044
00045 length=len;
00046 inner_degree=id;
00047 outer_degree=od;
00048
00049 SG_INFO( "LIK with parms: l=%d, id=%d, od=%d created!\n", len, id, od);
00050
00051 init(l, r);
00052 }
00053
00054 CLocalityImprovedStringKernel::~CLocalityImprovedStringKernel()
00055 {
00056 cleanup();
00057 }
00058
00059 bool CLocalityImprovedStringKernel::init(CFeatures* l, CFeatures* r)
00060 {
00061 CStringKernel<char>::init(l,r);
00062 return init_normalizer();
00063 }
00064
00065 float64_t CLocalityImprovedStringKernel::compute(int32_t idx_a, int32_t idx_b)
00066 {
00067 int32_t alen, blen;
00068 bool free_avec, free_bvec;
00069
00070 char* avec = ((CStringFeatures<char>*) lhs)->get_feature_vector(idx_a, alen, free_avec);
00071 char* bvec = ((CStringFeatures<char>*) rhs)->get_feature_vector(idx_b, blen, free_bvec);
00072
00073 ASSERT(alen==blen && alen>0);
00074
00075 int32_t i,t;
00076 float64_t* match=SG_MALLOC(float64_t, alen);
00077
00078
00079 for (i = 0; i<alen; i++)
00080 match[i] = (avec[i] == bvec[i])? 1 : 0;
00081
00082 float64_t outer_sum = 0;
00083
00084 for (t = 0; t<alen-length; t++)
00085 {
00086 float64_t sum = 0;
00087 for (i = 0; i<length && t+i+length+1<alen; i++)
00088 sum += (i+1)*match[t+i]+(length-i)*match[t+i+length+1];
00089
00090 float64_t inner_sum = (sum + (length+1)*match[t+length]) / ((2*length+1)*(length+1));
00091 inner_sum = pow(inner_sum, inner_degree + 1);
00092 outer_sum += inner_sum;
00093 }
00094 SG_FREE(match);
00095
00096 ((CStringFeatures<char>*) lhs)->free_feature_vector(avec, idx_a, free_avec);
00097 ((CStringFeatures<char>*) rhs)->free_feature_vector(bvec, idx_b, free_bvec);
00098 return pow(outer_sum, outer_degree + 1);
00099 }
00100
00101 void CLocalityImprovedStringKernel::init()
00102 {
00103 length = 0;
00104 inner_degree = 0;
00105 outer_degree = 0;
00106
00107 m_parameters->add(&length, "length", "Window Length.");
00108 m_parameters->add(&inner_degree, "inner_degree", "Inner degree.");
00109 m_parameters->add(&outer_degree, "outer_degree", "Outer degree.");
00110 }