VarianceKernelNormalizer.h

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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) 2009 Soeren Sonnenburg
00008  * Copyright (C) 2009 Fraunhofer Institute FIRST and Max-Planck-Society
00009  */
00010 
00011 #ifndef _VARIANCEKERNELNORMALIZER_H___
00012 #define _VARIANCEKERNELNORMALIZER_H___
00013 
00014 #include <shogun/kernel/KernelNormalizer.h>
00015 
00016 namespace shogun
00017 {
00027 class CVarianceKernelNormalizer : public CKernelNormalizer
00028 {
00029     public:
00032         CVarianceKernelNormalizer()
00033             : CKernelNormalizer(), meandiff(1.0), sqrt_meandiff(1.0)
00034         {
00035             m_parameters->add(&meandiff, "meandiff", "Scaling constant.");
00036             m_parameters->add(&sqrt_meandiff, "sqrt_meandiff",
00037                     "Square root of scaling constant.");
00038         }
00039 
00041         virtual ~CVarianceKernelNormalizer()
00042         {
00043         }
00044 
00047         virtual bool init(CKernel* k)
00048         {
00049             ASSERT(k);
00050             int32_t n=k->get_num_vec_lhs();
00051             ASSERT(n>0);
00052 
00053             CFeatures* old_lhs=k->lhs;
00054             CFeatures* old_rhs=k->rhs;
00055             k->lhs=old_lhs;
00056             k->rhs=old_lhs;
00057 
00058             float64_t diag_mean=0;
00059             float64_t overall_mean=0;
00060             for (int32_t i=0; i<n; i++)
00061             {
00062                 diag_mean+=k->compute(i, i);
00063 
00064                 for (int32_t j=0; j<n; j++)
00065                     overall_mean+=k->compute(i, j);
00066             }
00067             diag_mean/=n;
00068             overall_mean/=((float64_t) n)*n;
00069 
00070             k->lhs=old_lhs;
00071             k->rhs=old_rhs;
00072 
00073             meandiff=1.0/(diag_mean-overall_mean);
00074             sqrt_meandiff=CMath::sqrt(meandiff);
00075 
00076             return true;
00077         }
00078 
00084         inline virtual float64_t normalize(
00085             float64_t value, int32_t idx_lhs, int32_t idx_rhs)
00086         {
00087             return value*meandiff;
00088         }
00089 
00094         inline virtual float64_t normalize_lhs(float64_t value, int32_t idx_lhs)
00095         {
00096             return value*sqrt_meandiff;
00097         }
00098 
00103         inline virtual float64_t normalize_rhs(float64_t value, int32_t idx_rhs)
00104         {
00105             return value*sqrt_meandiff;
00106         }
00107 
00109         inline virtual const char* get_name() const { return "VarianceKernelNormalizer"; }
00110 
00111     protected:
00113         float64_t meandiff;
00115         float64_t sqrt_meandiff;
00116 };
00117 }
00118 #endif
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