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 <shogun/lib/common.h>
00012 #include <shogun/kernel/GaussianShortRealKernel.h>
00013 #include <shogun/features/Features.h>
00014 #include <shogun/features/SimpleFeatures.h>
00015 #include <shogun/io/SGIO.h>
00016 
00017 using namespace shogun;
00018 
00019 CGaussianShortRealKernel::CGaussianShortRealKernel()
00020 : CDotKernel(0), width(0.0)
00021 {
00022     register_params();
00023 }
00024 
00025 CGaussianShortRealKernel::CGaussianShortRealKernel(int32_t size, float64_t w)
00026 : CDotKernel(size), width(w)
00027 {
00028     register_params();
00029 }
00030 
00031 CGaussianShortRealKernel::CGaussianShortRealKernel(
00032     CSimpleFeatures<float32_t>* l, CSimpleFeatures<float32_t>* r, float64_t w, int32_t size)
00033 : CDotKernel(size), width(w)
00034 {
00035     init(l,r);
00036     register_params();
00037 }
00038 
00039 CGaussianShortRealKernel::~CGaussianShortRealKernel()
00040 {
00041 }
00042 
00043 bool CGaussianShortRealKernel::init(CFeatures* l, CFeatures* r)
00044 {
00045     CDotKernel::init(l, r);
00046     return init_normalizer();
00047 }
00048 
00049 float64_t CGaussianShortRealKernel::compute(int32_t idx_a, int32_t idx_b)
00050 {
00051     int32_t alen, blen;
00052     bool afree, bfree;
00053 
00054     float32_t* avec=((CSimpleFeatures<float32_t>*) lhs)->get_feature_vector(idx_a, alen, afree);
00055     float32_t* bvec=((CSimpleFeatures<float32_t>*) rhs)->get_feature_vector(idx_b, blen, bfree);
00056     ASSERT(alen==blen);
00057 
00058     float64_t result=0;
00059     for (int32_t i=0; i<alen; i++)
00060         result+=CMath::sq(avec[i]-bvec[i]);
00061 
00062     result=exp(-result/width);
00063 
00064     ((CSimpleFeatures<float32_t>*) lhs)->free_feature_vector(avec, idx_a, afree);
00065     ((CSimpleFeatures<float32_t>*) rhs)->free_feature_vector(bvec, idx_b, bfree);
00066 
00067     return result;
00068 }
00069 
00070 void CGaussianShortRealKernel::register_params()
00071 {
00072     m_parameters->add(&width, "width", "kernel width");
00073 }
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