FixedDegreeStringKernel.cpp
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00011 #include "lib/common.h"
00012 #include "kernel/FixedDegreeStringKernel.h"
00013 #include "features/Features.h"
00014 #include "features/StringFeatures.h"
00015 #include "lib/io.h"
00016
00017 CFixedDegreeStringKernel::CFixedDegreeStringKernel(INT size, INT d)
00018 : CStringKernel<CHAR>(size), degree(d), sqrtdiag_lhs(NULL),
00019 sqrtdiag_rhs(NULL), initialized(false)
00020 {
00021 }
00022
00023 CFixedDegreeStringKernel::CFixedDegreeStringKernel(
00024 CStringFeatures<CHAR>* l, CStringFeatures<CHAR>* r, INT d)
00025 : CStringKernel<CHAR>(10), degree(d), sqrtdiag_lhs(NULL),
00026 sqrtdiag_rhs(NULL), initialized(false)
00027 {
00028 init(l, r);
00029 }
00030
00031 CFixedDegreeStringKernel::~CFixedDegreeStringKernel()
00032 {
00033 cleanup();
00034 }
00035
00036 bool CFixedDegreeStringKernel::init(CFeatures* l, CFeatures* r)
00037 {
00038 bool result = CStringKernel<CHAR>::init(l, r);
00039 initialized = false;
00040
00041 if (sqrtdiag_lhs!=sqrtdiag_rhs)
00042 delete[] sqrtdiag_rhs;
00043 sqrtdiag_rhs=NULL;
00044 delete[] sqrtdiag_lhs;
00045 sqrtdiag_lhs=new DREAL[lhs->get_num_vectors()];
00046
00047 if (l==r)
00048 sqrtdiag_rhs=sqrtdiag_lhs;
00049 else
00050 sqrtdiag_rhs=new DREAL[rhs->get_num_vectors()];
00051
00052 this->lhs=(CStringFeatures<CHAR>*) l;
00053 this->rhs=(CStringFeatures<CHAR>*) l;
00054
00055 CKernel::init_sqrt_diag(sqrtdiag_lhs, lhs->get_num_vectors());
00056
00057
00058 if (sqrtdiag_lhs!=sqrtdiag_rhs)
00059 {
00060 this->lhs = (CStringFeatures<CHAR>*) r;
00061 this->rhs = (CStringFeatures<CHAR>*) r;
00062 CKernel::init_sqrt_diag(sqrtdiag_rhs, rhs->get_num_vectors());
00063 }
00064
00065 this->lhs = (CStringFeatures<CHAR>*) l;
00066 this->rhs = (CStringFeatures<CHAR>*) r;
00067
00068 initialized = true;
00069 return result;
00070 }
00071
00072 void CFixedDegreeStringKernel::cleanup()
00073 {
00074 if (sqrtdiag_lhs != sqrtdiag_rhs)
00075 delete[] sqrtdiag_rhs;
00076 sqrtdiag_rhs = NULL;
00077
00078 delete[] sqrtdiag_lhs;
00079 sqrtdiag_lhs = NULL;
00080
00081 initialized = false;
00082
00083 CKernel::cleanup();
00084 }
00085
00086 bool CFixedDegreeStringKernel::load_init(FILE* src)
00087 {
00088 return false;
00089 }
00090
00091 bool CFixedDegreeStringKernel::save_init(FILE* dest)
00092 {
00093 return false;
00094 }
00095
00096 DREAL CFixedDegreeStringKernel::compute(INT idx_a, INT idx_b)
00097 {
00098 INT alen, blen;
00099
00100 CHAR* avec = ((CStringFeatures<CHAR>*) lhs)->get_feature_vector(idx_a, alen);
00101 CHAR* bvec = ((CStringFeatures<CHAR>*) rhs)->get_feature_vector(idx_b, blen);
00102
00103 ASSERT(alen==blen);
00104
00105 DREAL sqrt = initialized ? (sqrtdiag_lhs[idx_a]*sqrtdiag_rhs[idx_b]) : 1.0;
00106 LONG sum = 0;
00107 for (INT i = 0; i<alen-degree+1; i++)
00108 {
00109 bool match = true;
00110
00111 for (INT j = i; j<i+degree && match; j++)
00112 match = avec[j]==bvec[j];
00113 if (match)
00114 sum++;
00115 }
00116 return (DREAL) sum/sqrt;
00117 }