SqrtDiagKernelNormalizer.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 _SQRTDIAGKERNELNORMALIZER_H___
00012 #define _SQRTDIAGKERNELNORMALIZER_H___
00013 
00014 #include "kernel/KernelNormalizer.h"
00015 #include "kernel/CommWordStringKernel.h"
00016 
00017 namespace shogun
00018 {
00029 class CSqrtDiagKernelNormalizer : public CKernelNormalizer
00030 {
00031     public:
00036         CSqrtDiagKernelNormalizer(bool use_opt_diag=false): sqrtdiag_lhs(NULL),
00037             sqrtdiag_rhs(NULL), use_optimized_diagonal_computation(use_opt_diag)
00038         {
00039         }
00040 
00042         virtual ~CSqrtDiagKernelNormalizer()
00043         {
00044             delete[] sqrtdiag_lhs;
00045             delete[] sqrtdiag_rhs;
00046         }
00047 
00050         virtual bool init(CKernel* k)
00051         {
00052             ASSERT(k);
00053             int32_t num_lhs=k->get_num_vec_lhs();
00054             int32_t num_rhs=k->get_num_vec_rhs();
00055             ASSERT(num_lhs>0);
00056             ASSERT(num_rhs>0);
00057 
00058             CFeatures* old_lhs=k->lhs;
00059             CFeatures* old_rhs=k->rhs;
00060 
00061             k->lhs=old_lhs;
00062             k->rhs=old_lhs;
00063             bool r1=alloc_and_compute_diag(k, sqrtdiag_lhs, num_lhs);
00064 
00065             k->lhs=old_rhs;
00066             k->rhs=old_rhs;
00067             bool r2=alloc_and_compute_diag(k, sqrtdiag_rhs, num_rhs);
00068 
00069             k->lhs=old_lhs;
00070             k->rhs=old_rhs;
00071 
00072             return r1 && r2;
00073         }
00074 
00080         inline virtual float64_t normalize(
00081             float64_t value, int32_t idx_lhs, int32_t idx_rhs)
00082         {
00083             float64_t sqrt_both=sqrtdiag_lhs[idx_lhs]*sqrtdiag_rhs[idx_rhs];
00084             return value/sqrt_both;
00085         }
00086 
00091         inline virtual float64_t normalize_lhs(float64_t value, int32_t idx_lhs)
00092         {
00093             return value/sqrtdiag_lhs[idx_lhs];
00094         }
00095 
00100         inline virtual float64_t normalize_rhs(float64_t value, int32_t idx_rhs)
00101         {
00102             return value/sqrtdiag_rhs[idx_rhs];
00103         }
00104 
00105     public:
00110         bool alloc_and_compute_diag(CKernel* k, float64_t* &v, int32_t num)
00111         {
00112             delete[] v;
00113             v=new float64_t[num];
00114 
00115             for (int32_t i=0; i<num; i++)
00116             {
00117                 if (k->get_kernel_type() == K_COMMWORDSTRING)
00118                 {
00119                     if (use_optimized_diagonal_computation)
00120                         v[i]=sqrt(((CCommWordStringKernel*) k)->compute_diag(i));
00121                     else
00122                         v[i]=sqrt(((CCommWordStringKernel*) k)->compute_helper(i,i, true));
00123                 }
00124                 else
00125                     v[i]=sqrt(k->compute(i,i));
00126 
00127                 if (v[i]==0.0)
00128                     v[i]=1e-16; /* avoid divide by zero exception */
00129             }
00130 
00131             return (v!=NULL);
00132         }
00133 
00135         inline virtual const char* get_name() const { return "SqrtDiagKernelNormalizer"; }
00136 
00137     protected:
00139         float64_t* sqrtdiag_lhs;
00141         float64_t* sqrtdiag_rhs;
00143         bool use_optimized_diagonal_computation;
00144 };
00145 }
00146 #endif

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