PLearn 0.1
NegCrossEntropySigmoidVariable.cc
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00001 // -*- C++ -*-
00002 
00003 // PLearn (A C++ Machine Learning Library)
00004 // Copyright (C) 1998 Pascal Vincent
00005 // Copyright (C) 1999-2002 Pascal Vincent, Yoshua Bengio, Rejean Ducharme and University of Montreal
00006 // Copyright (C) 2001-2002 Nicolas Chapados, Ichiro Takeuchi, Jean-Sebastien Senecal
00007 // Copyright (C) 2002 Xiangdong Wang, Christian Dorion
00008 // Copyright (C) 2003 Olivier Delalleau
00009 
00010 // Redistribution and use in source and binary forms, with or without
00011 // modification, are permitted provided that the following conditions are met:
00012 // 
00013 //  1. Redistributions of source code must retain the above copyright
00014 //     notice, this list of conditions and the following disclaimer.
00015 // 
00016 //  2. Redistributions in binary form must reproduce the above copyright
00017 //     notice, this list of conditions and the following disclaimer in the
00018 //     documentation and/or other materials provided with the distribution.
00019 // 
00020 //  3. The name of the authors may not be used to endorse or promote
00021 //     products derived from this software without specific prior written
00022 //     permission.
00023 // 
00024 // THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
00025 // IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
00026 // OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN
00027 // NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
00028 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
00029 // TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
00030 // PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
00031 // LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
00032 // NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
00033 // SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
00034 // 
00035 // This file is part of the PLearn library. For more information on the PLearn
00036 // library, go to the PLearn Web site at www.plearn.org
00037 
00038 
00039 /* *******************************************************      
00040  * $Id: NegCrossEntropySigmoidVariable.cc 8376 2008-01-10 15:08:15Z saintmlx $
00041  * This file is part of the PLearn library.
00042  ******************************************************* */
00043 
00044 #include "NegCrossEntropySigmoidVariable.h"
00045 
00046 namespace PLearn {
00047 using namespace std;
00048 
00051 PLEARN_IMPLEMENT_OBJECT(NegCrossEntropySigmoidVariable,
00052                         "Compute sigmoid of its first input, and then computes the negative "
00053                         "cross-entropy cost",
00054                         "Let o the first input ant t te second input, this computes\n"
00055                         "result = - \\sum_i t_i*log(o_i) + (1-t_i)*log(1-o_i)");
00056 
00058 // NegCrossEntropySigmoidVariable //
00060 NegCrossEntropySigmoidVariable::NegCrossEntropySigmoidVariable(Variable* netout, Variable* target, real regularizer_, bool ignore_missing_)
00061     : inherited(netout,target,1,1),regularizer(regularizer_), ignore_missing(ignore_missing_)
00062 {
00063     build_();
00064 }
00065 
00067 // declareOptions //
00069 void NegCrossEntropySigmoidVariable::declareOptions(OptionList& ol)
00070 {
00071     declareOption(ol, "regularizer", &NegCrossEntropySigmoidVariable::regularizer, OptionBase::buildoption, 
00072                   "If > 0, will modify the cost function to: \n"
00073                   "(1-t)(r*log(o)+(1-r)*log(1-o)) + t*(r*log(1-o)+(1-r)*log(o)) \n"
00074                   "(t = target, o = output, r = regularizer = a small value)\n");
00075 
00076     declareOption(ol, "ignore_missing", &NegCrossEntropySigmoidVariable::ignore_missing, OptionBase::buildoption, 
00077                   "Indication that missing targets should be ignored");
00078 
00079     inherited::declareOptions(ol);
00080 }
00081 
00083 // build //
00085 void NegCrossEntropySigmoidVariable::build()
00086 {
00087     inherited::build();
00088     build_();
00089 }
00090 
00091 void NegCrossEntropySigmoidVariable::build_()
00092 {
00093     if (input1 && input2) {
00094         // input1 and input2 are (respectively) netout and target from constructor
00095         if(input1->size() != input2->size())
00096             PLERROR("In NegCrossEntropySigmoidVariable: netout and target must have the same size");
00097     }
00098 }
00099 
00101 // recomputeSize //
00103 void NegCrossEntropySigmoidVariable::recomputeSize(int& l, int& w) const
00104 { l=1, w=1; }
00105 
00107 // fprop //
00109 void NegCrossEntropySigmoidVariable::fprop()
00110 {
00111     real cost = 0.0;
00112     for (int i=0; i<input1->size(); i++)
00113     {
00114         real output = sigmoid(input1->valuedata[i]);
00115         real target = input2->valuedata[i];
00116         if(!ignore_missing || !is_missing(target))
00117         {
00118             if (fast_exact_is_equal(output,0.0)) {
00119                 if (fast_exact_is_equal(target, 1.0)) {
00120                     PLWARNING("NegCrossEntropySigmoidVariable::fprop: model output is 0 and target is 1, cost should be infinite !");
00121                     cost += -1e9;
00122                 } // If target == 0.0 do nothing, cost is 0.
00123             } else if (fast_exact_is_equal(output, 1.0)) {
00124                 if (fast_exact_is_equal(target, 0.0)) {
00125                     PLWARNING("NegCrossEntropySigmoidVariable::fprop: model output is 1 and target is 0, cost should be infinite !");
00126                     cost += -1e9;
00127                 } // If target == 1.0 do nothing, cost is 0.
00128             } else {
00129                 if (fast_exact_is_equal(regularizer, 0)) {
00130                     // Standard cross entropy.
00131                     cost += target*pl_log(output) + (1.0-target)*pl_log(1.0-output);
00132                 } else {
00133                     // Regularized cross entropy.
00134                     cost += target*((1 - regularizer) * pl_log(output) + regularizer * pl_log(1.0 - output)) +
00135                         (1.0-target)*((1 - regularizer) * pl_log(1.0-output) + regularizer * pl_log(output));
00136                 }
00137             }
00138         }
00139     }
00140     valuedata[0] = -cost;
00141 }
00142 
00144 // bprop //
00146 void NegCrossEntropySigmoidVariable::bprop()
00147 {
00148     real gr = *gradientdata;
00149     for (int i=0; i<input1->size(); i++)
00150     {
00151         real output = sigmoid(input1->valuedata[i]);
00152         real target = input2->valuedata[i];
00153         if(!ignore_missing || !is_missing(target))
00154         {
00155 
00156             if (fast_exact_is_equal(regularizer, 0)) {
00157                 // Standard cross entropy.
00158                 input1->gradientdata[i] += gr*(output - target);
00159             } else {
00160                 // Regularized cross entropy.
00161                 if (fast_exact_is_equal(target, 0.0)) {
00162                     input1->gradientdata[i] += gr*((1-regularizer) * output - regularizer * (1-output));
00163                 } else if (fast_exact_is_equal(target, 1.0)) {
00164                     input1->gradientdata[i] += gr*(regularizer * output - (1-regularizer) * (1-output));
00165                 } else {
00166                     PLERROR("NegCrossEntropySigmoidVariable::bprop: target is neither 0 nor 1");
00167                 }
00168             }
00169         }
00170     }
00171 }
00172 
00174 // setRegularizer //
00176 void NegCrossEntropySigmoidVariable::setRegularizer(real r)
00177 {
00178     PLWARNING("NegCrossEntropySigmoidVariable::setRegularizer() has been deprecated, use the setOption() method instead");
00179     this->regularizer = r;
00180 }
00181 
00182 } // end of namespace PLearn
00183 
00184 
00185 /*
00186   Local Variables:
00187   mode:c++
00188   c-basic-offset:4
00189   c-file-style:"stroustrup"
00190   c-file-offsets:((innamespace . 0)(inline-open . 0))
00191   indent-tabs-mode:nil
00192   fill-column:79
00193   End:
00194 */
00195 // vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:encoding=utf-8:textwidth=79 :
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