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 "lib/common.h"
00012 #include "kernel/GaussianShiftKernel.h"
00013 #include "features/Features.h"
00014 #include "features/SimpleFeatures.h"
00015 #include "lib/io.h"
00016 
00017 using namespace shogun;
00018 
00019 CGaussianShiftKernel::CGaussianShiftKernel(
00020     int32_t size, float64_t w, int32_t ms, int32_t ss)
00021 : CGaussianKernel(size, w), max_shift(ms), shift_step(ss)
00022 {
00023 }
00024 
00025 CGaussianShiftKernel::CGaussianShiftKernel(
00026     CSimpleFeatures<float64_t>* l, CSimpleFeatures<float64_t>* r, float64_t w, int32_t ms, int32_t ss,
00027     int32_t size)
00028 : CGaussianKernel(l, r, w, size), max_shift(ms), shift_step(ss)
00029 {
00030     init(l,r);
00031 }
00032 
00033 CGaussianShiftKernel::~CGaussianShiftKernel()
00034 {
00035 }
00036 
00037 float64_t CGaussianShiftKernel::compute(int32_t idx_a, int32_t idx_b)
00038 {
00039     int32_t alen, blen;
00040     bool afree, bfree;
00041 
00042     float64_t* avec=
00043         ((CSimpleFeatures<float64_t>*) lhs)->get_feature_vector(idx_a, alen, afree);
00044     float64_t* bvec=
00045         ((CSimpleFeatures<float64_t>*) rhs)->get_feature_vector(idx_b, blen, bfree);
00046     ASSERT(alen==blen);
00047 
00048     float64_t result = 0.0 ;
00049     float64_t sum=0.0 ;
00050     for (int32_t i=0; i<alen; i++)
00051         sum+=(avec[i]-bvec[i])*(avec[i]-bvec[i]);
00052     result += exp(-sum/width) ;
00053 
00054     for (int32_t shift = shift_step, s=1; shift<max_shift; shift+=shift_step, s++)
00055     {
00056         sum=0.0 ;
00057         for (int32_t i=0; i<alen-shift; i++)
00058             sum+=(avec[i+shift]-bvec[i])*(avec[i+shift]-bvec[i]);
00059         result += exp(-sum/width)/(2*s) ;
00060 
00061         sum=0.0 ;
00062         for (int32_t i=0; i<alen-shift; i++)
00063             sum+=(avec[i]-bvec[i+shift])*(avec[i]-bvec[i+shift]);
00064         result += exp(-sum/width)/(2*s) ;
00065     }
00066 
00067     ((CSimpleFeatures<float64_t>*) lhs)->free_feature_vector(avec, idx_a, afree);
00068     ((CSimpleFeatures<float64_t>*) rhs)->free_feature_vector(bvec, idx_b, bfree);
00069 
00070     return result;
00071 }
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