LeakyIntegrator.H

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00001 /*!@file Neuro/LeakyIntegrator.H Class declarations for a leaky integrator neuron */
00002 
00003 // //////////////////////////////////////////////////////////////////// //
00004 // The iLab Neuromorphic Vision C++ Toolkit - Copyright (C) 2001 by the //
00005 // University of Southern California (USC) and the iLab at USC.         //
00006 // See http://iLab.usc.edu for information about this project.          //
00007 // //////////////////////////////////////////////////////////////////// //
00008 // Major portions of the iLab Neuromorphic Vision Toolkit are protected //
00009 // under the U.S. patent ``Computation of Intrinsic Perceptual Saliency //
00010 // in Visual Environments, and Applications'' by Christof Koch and      //
00011 // Laurent Itti, California Institute of Technology, 2001 (patent       //
00012 // pending; application number 09/912,225 filed July 23, 2001; see      //
00013 // http://pair.uspto.gov/cgi-bin/final/home.pl for current status).     //
00014 // //////////////////////////////////////////////////////////////////// //
00015 // This file is part of the iLab Neuromorphic Vision C++ Toolkit.       //
00016 //                                                                      //
00017 // The iLab Neuromorphic Vision C++ Toolkit is free software; you can   //
00018 // redistribute it and/or modify it under the terms of the GNU General  //
00019 // Public License as published by the Free Software Foundation; either  //
00020 // version 2 of the License, or (at your option) any later version.     //
00021 //                                                                      //
00022 // The iLab Neuromorphic Vision C++ Toolkit is distributed in the hope  //
00023 // that it will be useful, but WITHOUT ANY WARRANTY; without even the   //
00024 // implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR      //
00025 // PURPOSE.  See the GNU General Public License for more details.       //
00026 //                                                                      //
00027 // You should have received a copy of the GNU General Public License    //
00028 // along with the iLab Neuromorphic Vision C++ Toolkit; if not, write   //
00029 // to the Free Software Foundation, Inc., 59 Temple Place, Suite 330,   //
00030 // Boston, MA 02111-1307 USA.                                           //
00031 // //////////////////////////////////////////////////////////////////// //
00032 //
00033 // Primary maintainer for this file: Laurent Itti <itti@usc.edu>
00034 // $HeadURL: svn://isvn.usc.edu/software/invt/trunk/saliency/src/Neuro/LeakyIntegrator.H $
00035 // $Id: LeakyIntegrator.H 10729 2009-02-02 03:44:27Z itti $
00036 //
00037 
00038 #ifndef LEAKY_INTEGRATOR_H_DEFINED
00039 #define LEAKY_INTEGRATOR_H_DEFINED
00040 
00041 #include "Util/SimTime.H"
00042 
00043 // ######################################################################
00044 //! A leaky integrator neuron, used by standard saliency map (SM)
00045 // ######################################################################
00046 /*! This is the saliency map neuron used in conjunction with SM which is
00047   a 2D array of LeakyIntegrator. */
00048 class LeakyIntegrator
00049 {
00050 public:
00051   //! constructor
00052   /*! Constructor with default params
00053     @param timeStep is the integration time step, in s
00054     @param C is the membrane capacitance, in Farads
00055     @param Gleak is the leak conductance, in Siemens
00056     @param GinhDecay decay factor applied to Ginh at every time step */
00057   inline LeakyIntegrator(const SimTime timeStep = SimTime::SECS(0.0001),
00058                          const float C = 5.0E-8F,
00059                          const float Gleak = 1.0E-7F,
00060                          const float GinhDecay = 0.9999F);
00061 
00062   //! set input current (A)
00063   inline void input(const float current);
00064 
00065   //! reset membrane potential to given value (in Volts)
00066   inline void resetV(const double val);
00067 
00068   //! integrate for up to given time (in s)
00069   inline void integrate(const SimTime& t);
00070 
00071   //! get current membrane potential (in V)
00072   inline float getV() const;
00073 
00074   //! set inhibitory conductance (S)
00075   inline void setGinh(const float g);
00076 
00077   //! add to inhibitory conductance (S)
00078   inline void addGinh(const float g);
00079 
00080   //! set the decay factor for Ginh
00081   inline void setGinhDecay(const float decay);
00082 
00083 private:
00084   SimTime itsTimeStep;// time step to use for difference equations (in s)
00085   float itsV;         // membrane potential in Volts
00086   float itsI;         // input current in Amperes
00087   float itsGinh;      // inhibitory conductance in Siemens
00088   float itsGinhDecay; // per time step decay factor on Ginh
00089   float itsC;         // capacitance in Farads
00090   float itsGleak;     // leak conductance in Siemens
00091   SimTime itsT;       // time of last integration
00092 };
00093 
00094 // ######################################################################
00095 // ##### Inline functions for LeakyIntegrator:
00096 // ######################################################################
00097 
00098 inline LeakyIntegrator::LeakyIntegrator(const SimTime timeStep,
00099                                         const float C,
00100                                         const float Gleak,
00101                                         const float GinhDecay) :
00102   itsTimeStep(timeStep), itsV(0.0F), itsI(0.0F), itsGinh(0.0F),
00103   itsGinhDecay(GinhDecay), itsC(C), itsGleak(Gleak), itsT(SimTime::ZERO())
00104 {  }
00105 
00106 // ######################################################################
00107 inline void LeakyIntegrator::input(const float current)
00108 { itsI = current; }
00109 
00110 // ######################################################################
00111 inline void LeakyIntegrator::resetV(const double val)
00112 { itsV = val; }
00113 
00114 // ######################################################################
00115 inline void LeakyIntegrator::integrate(const SimTime& t)
00116 {
00117   // we run our difference equations with a time step of itsTimeStep;
00118   // let's here figure out how many iterations we will need to go from
00119   // itsT to t. We will iterate for a number of equal steps, with each
00120   // step as close to itsTimeStep as possible to that we end up at
00121   // time t after iterating for an integer number of time steps:
00122   const SimTime dt = SimTime::computeDeltaT((t - itsT), itsTimeStep);
00123   const float dtsc = float(dt.secs()) / itsC;
00124 
00125   for (SimTime tt = itsT; tt < t; tt += dt)
00126     {
00127       itsV += dtsc * ( itsI - ( itsGleak + itsGinh ) * itsV );
00128       if (itsV < 0.0F) itsV = 0.0F;
00129       itsGinh *= itsGinhDecay; // progressively loose inhibitory influences
00130     }
00131 
00132   // we are done, just keep track of new current time:
00133   itsT = t;
00134 }
00135 
00136 // ######################################################################
00137 inline float LeakyIntegrator::getV() const
00138 { return itsV; }
00139 
00140 // ######################################################################
00141 inline void LeakyIntegrator::setGinh(const float g)
00142 { itsGinh = g; }
00143 
00144 // ######################################################################
00145 inline void LeakyIntegrator::addGinh(const float g)
00146 { itsGinh += g; }
00147 
00148 // ######################################################################
00149 inline void LeakyIntegrator::setGinhDecay(const float decay)
00150 { itsGinhDecay = decay; }
00151 
00152 #endif
00153 
00154 // ######################################################################
00155 /* So things look consistent in everyone's emacs... */
00156 /* Local Variables: */
00157 /* indent-tabs-mode: nil */
00158 /* End: */
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