SigmoidKernel.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) 1999-2010 Soeren Sonnenburg
00008  * Copyright (C) 1999-2009 Fraunhofer Institute FIRST and Max-Planck-Society
00009  * Copyright (C) 2010 Berlin Institute of Technology
00010  */
00011 
00012 #ifndef _SIGMOIDKERNEL_H___
00013 #define _SIGMOIDKERNEL_H___
00014 
00015 #include <shogun/lib/common.h>
00016 #include <shogun/kernel/DotKernel.h>
00017 #include <shogun/features/DotFeatures.h>
00018 
00019 namespace shogun
00020 {
00029 class CSigmoidKernel: public CDotKernel
00030 {
00031     public:
00033         CSigmoidKernel();
00034 
00041         CSigmoidKernel(int32_t size, float64_t gamma, float64_t coef0);
00042 
00051         CSigmoidKernel(CDotFeatures* l, CDotFeatures* r, int32_t size,
00052             float64_t gamma, float64_t coef0);
00053 
00054         virtual ~CSigmoidKernel();
00055 
00062         virtual bool init(CFeatures* l, CFeatures* r);
00063 
00065         virtual void cleanup();
00066 
00071         virtual EKernelType get_kernel_type() { return K_SIGMOID; }
00072 
00077         virtual const char* get_name() const { return "SigmoidKernel"; }
00078 
00079     protected:
00088         inline virtual float64_t compute(int32_t idx_a, int32_t idx_b)
00089         {
00090             return tanh(gamma*CDotKernel::compute(idx_a,idx_b)+coef0);
00091         }
00092 
00093     private:
00094         void init();
00095 
00096     protected:
00098         float64_t gamma;
00100         float64_t coef0;
00101 };
00102 }
00103 #endif /* _SIGMOIDKERNEL_H__ */
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