LocalityImprovedStringKernel.cpp
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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 CLocalityImprovedStringKernel::CLocalityImprovedStringKernel(
00018 INT size, INT l, INT id, INT od)
00019 : CStringKernel<CHAR>(size), length(l), inner_degree(id), outer_degree(od)
00020 {
00021 SG_INFO( "LIK with parms: l=%d, id=%d, od=%d created!\n", l, id, od);
00022 }
00023
00024 CLocalityImprovedStringKernel::CLocalityImprovedStringKernel(
00025 CStringFeatures<CHAR>* l, CStringFeatures<CHAR>* r, INT len, INT id, INT od)
00026 : CStringKernel<CHAR>(10), length(len), inner_degree(id), outer_degree(od)
00027 {
00028 SG_INFO( "LIK with parms: l=%d, id=%d, od=%d created!\n", len, id, od);
00029
00030 init(l, r);
00031 }
00032
00033 CLocalityImprovedStringKernel::~CLocalityImprovedStringKernel()
00034 {
00035 cleanup();
00036 }
00037
00038 bool CLocalityImprovedStringKernel::init(CFeatures* l, CFeatures* r)
00039 {
00040 return CStringKernel<CHAR>::init(l,r);
00041 }
00042
00043 bool CLocalityImprovedStringKernel::load_init(FILE* src)
00044 {
00045 return false;
00046 }
00047
00048 bool CLocalityImprovedStringKernel::save_init(FILE* dest)
00049 {
00050 return false;
00051 }
00052
00053 DREAL CLocalityImprovedStringKernel::compute(INT idx_a, INT idx_b)
00054 {
00055 INT alen, blen;
00056
00057 CHAR* avec = ((CStringFeatures<CHAR>*) lhs)->get_feature_vector(idx_a, alen);
00058 CHAR* bvec = ((CStringFeatures<CHAR>*) rhs)->get_feature_vector(idx_b, blen);
00059
00060 ASSERT(alen==blen && alen>0);
00061
00062 INT i,t;
00063 DREAL* match=new DREAL[alen];
00064
00065
00066 for (i = 0; i<alen; i++)
00067 match[i] = (avec[i] == bvec[i])? 1 : 0;
00068
00069 DREAL outer_sum = 0;
00070
00071 for (t = 0; t<alen-length; t++)
00072 {
00073 DREAL sum = 0;
00074 for (i = 0; i<length && t+i+length+1<alen; i++)
00075 sum += (i+1)*match[t+i]+(length-i)*match[t+i+length+1];
00076
00077 DREAL inner_sum = (sum + (length+1)*match[t+length]) / ((2*length+1)*(length+1));
00078 inner_sum = pow(inner_sum, inner_degree + 1);
00079 outer_sum += inner_sum;
00080 }
00081 delete[] match;
00082 return pow(outer_sum, outer_degree + 1);
00083 }