Chi2Kernel.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) 1999-2008 Soeren Sonnenburg
00008  * Copyright (C) 1999-2008 Fraunhofer Institute FIRST and Max-Planck-Society
00009  */
00010 
00011 #include "lib/common.h"
00012 #include "kernel/Chi2Kernel.h"
00013 #include "features/Features.h"
00014 #include "features/RealFeatures.h"
00015 #include "lib/io.h"
00016 
00017 CChi2Kernel::CChi2Kernel(INT size, DREAL w)
00018 : CSimpleKernel<DREAL>(size), width(w)
00019 {
00020 }
00021 
00022 CChi2Kernel::CChi2Kernel(CRealFeatures* l, CRealFeatures* r, DREAL w, INT size)
00023 : CSimpleKernel<DREAL>(size), width(w)
00024 {
00025     init(l,r);
00026 }
00027 
00028 CChi2Kernel::~CChi2Kernel()
00029 {
00030     cleanup();
00031 }
00032 
00033 bool CChi2Kernel::init(CFeatures* l, CFeatures* r)
00034 {
00035     bool result=CSimpleKernel<DREAL>::init(l,r);
00036     return result;
00037 }
00038 
00039 bool CChi2Kernel::load_init(FILE* src)
00040 {
00041     return false;
00042 }
00043 
00044 bool CChi2Kernel::save_init(FILE* dest)
00045 {
00046     return false;
00047 }
00048   
00049 DREAL CChi2Kernel::compute(INT idx_a, INT idx_b)
00050 {
00051     INT alen, blen;
00052     bool afree, bfree;
00053 
00054     double* avec=((CRealFeatures*) lhs)->get_feature_vector(idx_a, alen, afree);
00055     double* bvec=((CRealFeatures*) rhs)->get_feature_vector(idx_b, blen, bfree);
00056     ASSERT(alen==blen);
00057 
00058     DREAL result=0;
00059     for (INT i=0; i<alen; i++)
00060     {
00061         DREAL n=avec[i]-bvec[i];
00062         DREAL d=avec[i]+bvec[i];
00063         if (d!=0)
00064             result+=n*n/d;
00065     }
00066 
00067     result=exp(-result/width);
00068 
00069     ((CRealFeatures*) lhs)->free_feature_vector(avec, idx_a, afree);
00070     ((CRealFeatures*) rhs)->free_feature_vector(bvec, idx_b, bfree);
00071 
00072     return result;
00073 }

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