GaussianShiftKernel.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 Gunnar Raetsch
00008  * Copyright (C) 2008-2009 Fraunhofer Institute FIRST and Max-Planck-Society
00009  */
00010 
00011 #include <shogun/lib/common.h>
00012 #include <shogun/kernel/GaussianShiftKernel.h>
00013 #include <shogun/features/Features.h>
00014 #include <shogun/io/SGIO.h>
00015 
00016 using namespace shogun;
00017 
00018 CGaussianShiftKernel::CGaussianShiftKernel()
00019 : CGaussianKernel(), max_shift(0), shift_step(0)
00020 {
00021     init();
00022 }
00023 
00024 CGaussianShiftKernel::CGaussianShiftKernel(
00025     int32_t size, float64_t w, int32_t ms, int32_t ss)
00026 : CGaussianKernel(size, w), max_shift(ms), shift_step(ss)
00027 {
00028     init();
00029 }
00030 
00031 CGaussianShiftKernel::CGaussianShiftKernel(
00032     CDenseFeatures<float64_t>* l, CDenseFeatures<float64_t>* r, float64_t w, int32_t ms, int32_t ss,
00033     int32_t size)
00034 : CGaussianKernel(l, r, w, size), max_shift(ms), shift_step(ss)
00035 {
00036     init();
00037     CGaussianKernel::init(l,r);
00038 }
00039 
00040 CGaussianShiftKernel::~CGaussianShiftKernel()
00041 {
00042 }
00043 
00044 float64_t CGaussianShiftKernel::compute(int32_t idx_a, int32_t idx_b)
00045 {
00046     int32_t alen, blen;
00047     bool afree, bfree;
00048 
00049     float64_t* avec=
00050         ((CDenseFeatures<float64_t>*) lhs)->get_feature_vector(idx_a, alen, afree);
00051     float64_t* bvec=
00052         ((CDenseFeatures<float64_t>*) rhs)->get_feature_vector(idx_b, blen, bfree);
00053     ASSERT(alen==blen);
00054 
00055     float64_t result = 0.0 ;
00056     float64_t sum=0.0 ;
00057     for (int32_t i=0; i<alen; i++)
00058         sum+=(avec[i]-bvec[i])*(avec[i]-bvec[i]);
00059     result += exp(-sum/width) ;
00060 
00061     for (int32_t shift = shift_step, s=1; shift<max_shift; shift+=shift_step, s++)
00062     {
00063         sum=0.0 ;
00064         for (int32_t i=0; i<alen-shift; i++)
00065             sum+=(avec[i+shift]-bvec[i])*(avec[i+shift]-bvec[i]);
00066         result += exp(-sum/width)/(2*s) ;
00067 
00068         sum=0.0 ;
00069         for (int32_t i=0; i<alen-shift; i++)
00070             sum+=(avec[i]-bvec[i+shift])*(avec[i]-bvec[i+shift]);
00071         result += exp(-sum/width)/(2*s) ;
00072     }
00073 
00074     ((CDenseFeatures<float64_t>*) lhs)->free_feature_vector(avec, idx_a, afree);
00075     ((CDenseFeatures<float64_t>*) rhs)->free_feature_vector(bvec, idx_b, bfree);
00076 
00077     return result;
00078 }
00079 
00080 void CGaussianShiftKernel::init()
00081 {
00082     SG_ADD(&max_shift, "max_shift", "Maximum shift.", MS_AVAILABLE);
00083     SG_ADD(&shift_step, "shift_step", "Shift stepsize.", MS_AVAILABLE);
00084 }
00085 
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