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src
shogun
kernel
JensenShannonKernel.cpp
Go to the documentation of this file.
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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) 2012 Viktor Gal
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* Copyright (C) 2012 Viktor Gal
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*/
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#include <
shogun/lib/common.h
>
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#include <
shogun/kernel/JensenShannonKernel.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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CJensenShannonKernel::CJensenShannonKernel
()
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:
CDotKernel
(0)
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{
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}
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CJensenShannonKernel::CJensenShannonKernel
(int32_t size)
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:
CDotKernel
(size)
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{
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}
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CJensenShannonKernel::CJensenShannonKernel
(
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CDenseFeatures<float64_t>
* l,
CDenseFeatures<float64_t>
* r, int32_t size)
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:
CDotKernel
(size)
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{
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init
(l,r);
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}
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CJensenShannonKernel::~CJensenShannonKernel
()
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{
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cleanup
();
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}
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bool
CJensenShannonKernel::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
CJensenShannonKernel::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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/* calcualte Jensen-Shannon kernel */
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for
(int32_t i=0; i<alen; i++) {
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float64_t
a_i = 0, b_i = 0;
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float64_t
ab = avec[i]+bvec[i];
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if
(avec[i] != 0)
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a_i = avec[i] *
CMath::log2
(ab/avec[i]);
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if
(bvec[i] != 0)
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b_i = bvec[i] * CMath::log2(ab/bvec[i]);
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result += 0.5*(a_i + b_i);
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}
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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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