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src
shogun
kernel
Chi2Kernel.cpp
浏览该文件的文档.
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/*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 3 of the License, or
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* (at your option) any later version.
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*
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* Written (W) 1999-2009 Soeren Sonnenburg
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* Copyright (C) 1999-2009 Fraunhofer Institute FIRST and Max-Planck-Society
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*/
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#include <
shogun/lib/common.h
>
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#include <
shogun/kernel/Chi2Kernel.h
>
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#include <
shogun/features/Features.h
>
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#include <
shogun/io/SGIO.h
>
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using namespace
shogun;
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void
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CChi2Kernel::init()
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{
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SG_ADD
(&
width
,
"width"
,
"Kernel width."
,
MS_AVAILABLE
);
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}
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CChi2Kernel::CChi2Kernel
()
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:
CDotKernel
(0), width(0)
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{
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init();
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}
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CChi2Kernel::CChi2Kernel
(int32_t size,
float64_t
w)
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:
CDotKernel
(size), width(w)
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{
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init();
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}
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CChi2Kernel::CChi2Kernel
(
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CDenseFeatures<float64_t>
* l,
CDenseFeatures<float64_t>
* r,
float64_t
w, int32_t size)
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:
CDotKernel
(size), width(w)
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{
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init();
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init(l,r);
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}
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CChi2Kernel::~CChi2Kernel
()
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{
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cleanup
();
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}
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bool
CChi2Kernel::init(
CFeatures
* l,
CFeatures
* r)
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{
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bool
result=CDotKernel::init(l,r);
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init_normalizer
();
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return
result;
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}
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float64_t
CChi2Kernel::compute
(int32_t idx_a, int32_t idx_b)
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{
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int32_t alen, blen;
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bool
afree, bfree;
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float64_t
* avec=
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((
CDenseFeatures<float64_t>
*)
lhs
)->get_feature_vector(idx_a, alen, afree);
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float64_t
* bvec=
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((
CDenseFeatures<float64_t>
*)
rhs
)->get_feature_vector(idx_b, blen, bfree);
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ASSERT
(alen==blen)
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float64_t
result=0;
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for
(int32_t i=0; i<alen; i++)
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{
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float64_t
n=avec[i]-bvec[i];
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float64_t
d=avec[i]+bvec[i];
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if
(d!=0)
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result+=n*n/d;
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}
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result=exp(-result/
width
);
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((
CDenseFeatures<float64_t>
*)
lhs
)->free_feature_vector(avec, idx_a, afree);
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((
CDenseFeatures<float64_t>
*)
rhs
)->free_feature_vector(bvec, idx_b, bfree);
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return
result;
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}
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float64_t
CChi2Kernel::get_width
()
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{
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return
width
;
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}
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CChi2Kernel
*
CChi2Kernel::obtain_from_generic
(
CKernel
* kernel)
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{
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if
(kernel->
get_kernel_type
()!=
K_CHI2
)
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{
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SG_SERROR
(
"Provided kernel is "
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"not of type CChi2Kernel!\n"
);
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}
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/* since an additional reference is returned */
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SG_REF
(kernel);
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return
(
CChi2Kernel
*)
kernel
;
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}
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