PLearn 0.1
SumEntropyOfBernoullis.cc
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00001 // -*- C++ -*-
00002 
00003 // SumEntropyOfBernoullis.cc
00004 //
00005 // Copyright (C) 2009 Pascal Vincent
00006 //
00007 // Redistribution and use in source and binary forms, with or without
00008 // modification, are permitted provided that the following conditions are met:
00009 //
00010 //  1. Redistributions of source code must retain the above copyright
00011 //     notice, this list of conditions and the following disclaimer.
00012 //
00013 //  2. Redistributions in binary form must reproduce the above copyright
00014 //     notice, this list of conditions and the following disclaimer in the
00015 //     documentation and/or other materials provided with the distribution.
00016 //
00017 //  3. The name of the authors may not be used to endorse or promote
00018 //     products derived from this software without specific prior written
00019 //     permission.
00020 //
00021 // THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
00022 // IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
00023 // OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN
00024 // NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
00025 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
00026 // TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
00027 // PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
00028 // LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
00029 // NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
00030 // SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
00031 //
00032 // This file is part of the PLearn library. For more information on the PLearn
00033 // library, go to the PLearn Web site at www.plearn.org
00034 
00035 // Authors: Pascal Vincent
00036 
00040 #include "SumEntropyOfBernoullis.h"
00041 
00042 namespace PLearn {
00043 using namespace std;
00044 
00047 PLEARN_IMPLEMENT_OBJECT(
00048     SumEntropyOfBernoullis,
00049     "Computes the sum of the entropies of independent Bernoulli variables whose parameters are given as input.",
00050     "i.e. if input is a matrix P, computes sum_ij - [P_ij log(P_ij) + (1-P_ij) log(1-P_ij)]"
00051     );
00052 
00053 SumEntropyOfBernoullis::SumEntropyOfBernoullis()
00054     : inherited(0, 1, 1)
00055 {
00056 }
00057 
00058 // constructor from input variable.
00059 SumEntropyOfBernoullis::SumEntropyOfBernoullis(Variable* input)
00060     : inherited(input, 1, 1)
00061 {
00062     build_();
00063 }
00064 
00065 // constructor from input variable and parameters
00066 // SumEntropyOfBernoullis::SumEntropyOfBernoullis(Variable* input, param_type the_parameter,...)
00067 // ### replace with actual parameters
00068 //  : inherited(input, this_variable_length, this_variable_width),
00069 //    parameter(the_parameter),
00070 //    ...
00071 //{
00072 //    // ### You may (or not) want to call build_() to finish building the
00073 //    // ### object
00074 //}
00075 
00076 void SumEntropyOfBernoullis::recomputeSize(int& l, int& w) const
00077 {
00078     l = w = 1;
00079 }
00080 
00081 // ### computes value from input's value
00082 void SumEntropyOfBernoullis::fprop()
00083 {
00084     double res = 0;
00085     Mat P = input->matValue;
00086     for(int i=0; i<P.length(); i++)
00087     {
00088         const real* P_i = P[i];
00089         for(int j=0; j<P.width(); j++)
00090         {
00091             double P_ij = P_i[j];
00092             if( (P_ij>1e-25) && ((1-P_ij)>1e-25) )
00093                 res -= P_ij*pl_log(P_ij) + (1-P_ij)*pl_log(1-P_ij);
00094         }
00095     }
00096     valuedata[0] = (real)res;
00097 }
00098 
00099 // ### computes input's gradient from gradient
00100 void SumEntropyOfBernoullis::bprop()
00101 {
00102     /*
00103       -[p log(p) + (1-p) log(1-p)]' = -[log(p) + 1 - log(1-p) - 1 ]
00104                                     = log(1-p) - log(p)
00105     */
00106     real gr = gradientdata[0];
00107     Mat P = input->matValue;
00108     Mat Pgr = input->matGradient;
00109     for(int i=0; i<Pgr.length(); i++)
00110     {
00111         const real* P_i = P[i];
00112         real* Pgr_i = Pgr[i];
00113         for(int j=0; j<Pgr.width(); j++)
00114         {
00115             double P_ij = P_i[j];
00116             double one_minus_P_ij = 1-P_ij;
00117             if(P_ij<1e-25) 
00118                 P_ij = 1e-25;
00119             if(one_minus_P_ij<1e-25)
00120                 one_minus_P_ij = 1e-25;
00121             Pgr_i[j] += gr*( pl_log(one_minus_P_ij) - pl_log(P_ij) );
00122         }
00123     }
00124     
00125 
00126 }
00127 
00128 // ### You can implement these methods:
00129 // void SumEntropyOfBernoullis::bbprop() {}
00130 // void SumEntropyOfBernoullis::symbolicBprop() {}
00131 // void SumEntropyOfBernoullis::rfprop() {}
00132 
00133 
00134 // ### Nothing to add here, simply calls build_
00135 void SumEntropyOfBernoullis::build()
00136 {
00137     inherited::build();
00138     build_();
00139 }
00140 
00141 void SumEntropyOfBernoullis::makeDeepCopyFromShallowCopy(CopiesMap& copies)
00142 {
00143     inherited::makeDeepCopyFromShallowCopy(copies);
00144 }
00145 
00146 void SumEntropyOfBernoullis::declareOptions(OptionList& ol)
00147 {
00148     // ### Declare all of this object's options here.
00149     // ### For the "flags" of each option, you should typically specify
00150     // ### one of OptionBase::buildoption, OptionBase::learntoption or
00151     // ### OptionBase::tuningoption. If you don't provide one of these three,
00152     // ### this option will be ignored when loading values from a script.
00153     // ### You can also combine flags, for example with OptionBase::nosave:
00154     // ### (OptionBase::buildoption | OptionBase::nosave)
00155 
00156     // ### ex:
00157     // declareOption(ol, "myoption", &SumEntropyOfBernoullis::myoption,
00158     //               OptionBase::buildoption,
00159     //               "Help text describing this option");
00160     // ...
00161 
00162     // Now call the parent class' declareOptions
00163     inherited::declareOptions(ol);
00164 }
00165 
00166 void SumEntropyOfBernoullis::build_()
00167 {
00168     // ### This method should do the real building of the object,
00169     // ### according to set 'options', in *any* situation.
00170     // ### Typical situations include:
00171     // ###  - Initial building of an object from a few user-specified options
00172     // ###  - Building of a "reloaded" object: i.e. from the complete set of
00173     // ###    all serialised options.
00174     // ###  - Updating or "re-building" of an object after a few "tuning"
00175     // ###    options have been modified.
00176     // ### You should assume that the parent class' build_() has already been
00177     // ### called.
00178 }
00179 
00180 
00181 } // end of namespace PLearn
00182 
00183 
00184 /*
00185   Local Variables:
00186   mode:c++
00187   c-basic-offset:4
00188   c-file-style:"stroustrup"
00189   c-file-offsets:((innamespace . 0)(inline-open . 0))
00190   indent-tabs-mode:nil
00191   fill-column:79
00192   End:
00193 */
00194 // vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:encoding=utf-8:textwidth=79 :
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