MatchWordStringKernel.cpp

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00001 /*
00002  * This program is free software; you can redistribute it and/or modify
00003  * it under the terms of the GNU General Public License as published by
00004  * the Free Software Foundation; either version 3 of the License, or
00005  * (at your option) any later version.
00006  *
00007  * Written (W) 1999-2009 Soeren Sonnenburg
00008  * Copyright (C) 1999-2009 Fraunhofer Institute FIRST and Max-Planck-Society
00009  */
00010 
00011 #include "lib/common.h"
00012 #include "lib/Mathematics.h"
00013 #include "lib/io.h"
00014 #include "kernel/MatchWordStringKernel.h"
00015 #include "kernel/AvgDiagKernelNormalizer.h"
00016 #include "features/StringFeatures.h"
00017 
00018 using namespace shogun;
00019 
00020 CMatchWordStringKernel::CMatchWordStringKernel(int32_t size, int32_t d)
00021 : CStringKernel<uint16_t>(size), degree(d)
00022 {
00023     set_normalizer(new CAvgDiagKernelNormalizer());
00024 }
00025 
00026 CMatchWordStringKernel::CMatchWordStringKernel(CStringFeatures<uint16_t>* l, CStringFeatures<uint16_t>* r, int32_t d)
00027 : CStringKernel<uint16_t>(10), degree(d)
00028 {
00029     set_normalizer(new CAvgDiagKernelNormalizer());
00030     init(l, r);
00031 }
00032 
00033 CMatchWordStringKernel::~CMatchWordStringKernel()
00034 {
00035     cleanup();
00036 }
00037 
00038 bool CMatchWordStringKernel::init(CFeatures* l, CFeatures* r)
00039 {
00040     CStringKernel<uint16_t>::init(l, r);
00041     return init_normalizer();
00042 }
00043 
00044 float64_t CMatchWordStringKernel::compute(int32_t idx_a, int32_t idx_b)
00045 {
00046     int32_t alen, blen;
00047     bool free_avec, free_bvec;
00048 
00049     uint16_t* avec=((CStringFeatures<uint16_t>*) lhs)->get_feature_vector(idx_a, alen, free_avec);
00050     uint16_t* bvec=((CStringFeatures<uint16_t>*) rhs)->get_feature_vector(idx_b, blen, free_bvec);
00051     // can only deal with strings of same length
00052     ASSERT(alen==blen);
00053 
00054     float64_t sum=0;
00055     for (int32_t i=0; i<alen; i++)
00056         sum+= (avec[i]==bvec[i]) ? 1 : 0;
00057 
00058     ((CStringFeatures<uint16_t>*) lhs)->free_feature_vector(avec, idx_a, free_avec);
00059     ((CStringFeatures<uint16_t>*) rhs)->free_feature_vector(bvec, idx_b, free_bvec);
00060 
00061     return CMath::pow(sum, degree);
00062 }
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