GaussianShortRealKernel.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) 2008-2009 Soeren Sonnenburg
00008  * Copyright (C) 2008-2009 Fraunhofer Institute FIRST and Max-Planck-Society
00009  */
00010 
00011 #include "lib/common.h"
00012 #include "kernel/GaussianShortRealKernel.h"
00013 #include "features/Features.h"
00014 #include "features/SimpleFeatures.h"
00015 #include "lib/io.h"
00016 
00017 using namespace shogun;
00018 
00019 CGaussianShortRealKernel::CGaussianShortRealKernel(int32_t size, float64_t w)
00020 : CSimpleKernel<float32_t>(size), width(w)
00021 {
00022 }
00023 
00024 CGaussianShortRealKernel::CGaussianShortRealKernel(
00025     CSimpleFeatures<float32_t>* l, CSimpleFeatures<float32_t>* r, float64_t w, int32_t size)
00026 : CSimpleKernel<float32_t>(size), width(w)
00027 {
00028     init(l,r);
00029 }
00030 
00031 CGaussianShortRealKernel::~CGaussianShortRealKernel()
00032 {
00033 }
00034 
00035 bool CGaussianShortRealKernel::init(CFeatures* l, CFeatures* r)
00036 {
00037     CSimpleKernel<float32_t>::init(l, r);
00038     return init_normalizer();
00039 }
00040 
00041 float64_t CGaussianShortRealKernel::compute(int32_t idx_a, int32_t idx_b)
00042 {
00043     int32_t alen, blen;
00044     bool afree, bfree;
00045 
00046     float32_t* avec=((CSimpleFeatures<float32_t>*) lhs)->get_feature_vector(idx_a, alen, afree);
00047     float32_t* bvec=((CSimpleFeatures<float32_t>*) rhs)->get_feature_vector(idx_b, blen, bfree);
00048     ASSERT(alen==blen);
00049 
00050     float64_t result=0;
00051     for (int32_t i=0; i<alen; i++)
00052         result+=CMath::sq(avec[i]-bvec[i]);
00053 
00054     result=exp(-result/width);
00055 
00056     ((CSimpleFeatures<float32_t>*) lhs)->free_feature_vector(avec, idx_a, afree);
00057     ((CSimpleFeatures<float32_t>*) rhs)->free_feature_vector(bvec, idx_b, bfree);
00058 
00059     return result;
00060 }
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