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/features/SimpleFeatures.h>
00015 #include <shogun/io/SGIO.h>
00016 
00017 using namespace shogun;
00018 
00019 CGaussianShiftKernel::CGaussianShiftKernel()
00020 : CGaussianKernel(), max_shift(0), shift_step(0)
00021 {
00022     init();
00023 }
00024 
00025 CGaussianShiftKernel::CGaussianShiftKernel(
00026     int32_t size, float64_t w, int32_t ms, int32_t ss)
00027 : CGaussianKernel(size, w), max_shift(ms), shift_step(ss)
00028 {
00029     init();
00030 }
00031 
00032 CGaussianShiftKernel::CGaussianShiftKernel(
00033     CSimpleFeatures<float64_t>* l, CSimpleFeatures<float64_t>* r, float64_t w, int32_t ms, int32_t ss,
00034     int32_t size)
00035 : CGaussianKernel(l, r, w, size), max_shift(ms), shift_step(ss)
00036 {
00037     init();
00038     CGaussianKernel::init(l,r);
00039 }
00040 
00041 CGaussianShiftKernel::~CGaussianShiftKernel()
00042 {
00043 }
00044 
00045 float64_t CGaussianShiftKernel::compute(int32_t idx_a, int32_t idx_b)
00046 {
00047     int32_t alen, blen;
00048     bool afree, bfree;
00049 
00050     float64_t* avec=
00051         ((CSimpleFeatures<float64_t>*) lhs)->get_feature_vector(idx_a, alen, afree);
00052     float64_t* bvec=
00053         ((CSimpleFeatures<float64_t>*) rhs)->get_feature_vector(idx_b, blen, bfree);
00054     ASSERT(alen==blen);
00055 
00056     float64_t result = 0.0 ;
00057     float64_t sum=0.0 ;
00058     for (int32_t i=0; i<alen; i++)
00059         sum+=(avec[i]-bvec[i])*(avec[i]-bvec[i]);
00060     result += exp(-sum/width) ;
00061 
00062     for (int32_t shift = shift_step, s=1; shift<max_shift; shift+=shift_step, s++)
00063     {
00064         sum=0.0 ;
00065         for (int32_t i=0; i<alen-shift; i++)
00066             sum+=(avec[i+shift]-bvec[i])*(avec[i+shift]-bvec[i]);
00067         result += exp(-sum/width)/(2*s) ;
00068 
00069         sum=0.0 ;
00070         for (int32_t i=0; i<alen-shift; i++)
00071             sum+=(avec[i]-bvec[i+shift])*(avec[i]-bvec[i+shift]);
00072         result += exp(-sum/width)/(2*s) ;
00073     }
00074 
00075     ((CSimpleFeatures<float64_t>*) lhs)->free_feature_vector(avec, idx_a, afree);
00076     ((CSimpleFeatures<float64_t>*) rhs)->free_feature_vector(bvec, idx_b, bfree);
00077 
00078     return result;
00079 }
00080 
00081 void CGaussianShiftKernel::init()
00082 {
00083     m_parameters->add(&max_shift, "max_shift", "Maximum shift.");
00084     m_parameters->add(&shift_step, "shift_step", "Shift stepsize.");
00085 }
00086 
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