PLearn 0.1
DEPRECATED/RBMTruncExpLayer.cc
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00001 // -*- C++ -*-
00002 
00003 // RBMTruncExpLayer.cc
00004 //
00005 // Copyright (C) 2006 Pascal Lamblin & Dan Popovici
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 Lamblin & Dan Popovici
00036 
00039 #include "RBMTruncExpLayer.h"
00040 #include <plearn/math/TMat_maths.h>
00041 #include "RBMParameters.h"
00042 
00043 namespace PLearn {
00044 using namespace std;
00045 
00046 PLEARN_IMPLEMENT_OBJECT(
00047     RBMTruncExpLayer,
00048     "RBM Layer where unit distribution is a truncated exponential in [0,1]",
00049     "");
00050 
00051 RBMTruncExpLayer::RBMTruncExpLayer()
00052 {
00053 }
00054 
00055 RBMTruncExpLayer::RBMTruncExpLayer( int the_size )
00056 {
00057     size = the_size;
00058     units_types = string( the_size, 'l' );
00059     activations.resize( the_size );
00060     sample.resize( the_size );
00061     expectation.resize( the_size );
00062     expectation_is_up_to_date = false;
00063 }
00064 
00067 void RBMTruncExpLayer::getUnitActivations( int i, PP<RBMParameters> rbmp,
00068                                            int offset )
00069 {
00070     Vec activation = activations.subVec( i, 1 );
00071     rbmp->computeUnitActivations( i+offset, 1, activation );
00072     expectation_is_up_to_date = false;
00073 }
00074 
00077 void RBMTruncExpLayer::getAllActivations( PP<RBMParameters> rbmp, int offset )
00078 {
00079     rbmp->computeUnitActivations( offset, size, activations );
00080     expectation_is_up_to_date = false;
00081 }
00082 
00083 void RBMTruncExpLayer::generateSample()
00084 {
00085     /* The cumulative is :
00086      * C(U) = P(u<U | x) = (1 - exp(-U a)) / (1 - exp(-a)) if 0 < U < 1,
00087      *        0 if U <= 0 and
00088      *        1 if 1 <= U
00089      *
00090      * And the inverse, if 0 <= s <=1:
00091      * C^{-1}(s) = - log(1 - s*(1 - exp(-a)) / a
00092      */
00093 
00094     for( int i=0 ; i<size ; i++ )
00095     {
00096         real s = random_gen->uniform_sample();
00097         real a_i = activations[i];
00098         sample[i] = - pl_log( 1. - s*( 1 - exp(-a_i) ) ) / a_i;
00099     }
00100 }
00101 
00102 void RBMTruncExpLayer::computeExpectation()
00103 {
00104     if( expectation_is_up_to_date )
00105         return;
00106 
00107     /* Conditional expectation:
00108      * E[u|x] = 1/(1-exp(a)) + 1/a
00109      */
00110 
00111     for( int i=0 ; i<size ; i++ )
00112     {
00113         real a_i = activations[i];
00114         expectation[i] = 1/(1-exp(a_i)) + 1/a_i;
00115     }
00116 
00117     expectation_is_up_to_date = true;
00118 }
00119 
00120 void RBMTruncExpLayer::bpropUpdate(const Vec& input, const Vec& output,
00121                                    Vec& input_gradient,
00122                                    const Vec& output_gradient)
00123 {
00124     PLASSERT( input.size() == size );
00125     PLASSERT( output.size() == size );
00126     PLASSERT( output_gradient.size() == size );
00127     input_gradient.resize( size );
00128 
00129     // df/da = exp(a)/(1-exp(a))^2 - 1/a^2
00130 
00131     for( int i=0 ; i<size ; i++ )
00132     {
00133         real a_i = input[i];
00134         real ea_i = exp( a_i );
00135         input_gradient[i] = ea_i/( (1 - ea_i) * (1 - ea_i) ) + 1/(a_i * a_i);
00136     }
00137 }
00138 
00139 
00140 
00141 void RBMTruncExpLayer::declareOptions(OptionList& ol)
00142 {
00143 /*
00144     declareOption(ol, "size", &RBMTruncExpLayer::size,
00145                   OptionBase::buildoption,
00146                   "Number of units.");
00147 */
00148     // Now call the parent class' declareOptions
00149     inherited::declareOptions(ol);
00150 }
00151 
00152 void RBMTruncExpLayer::build_()
00153 {
00154     if( size < 0 )
00155         size = int(units_types.size());
00156     if( size != (int) units_types.size() )
00157         units_types = string( size, 'l' );
00158 
00159     activations.resize( size );
00160     sample.resize( size );
00161     expectation.resize( size );
00162     expectation_is_up_to_date = false;
00163 }
00164 
00165 void RBMTruncExpLayer::build()
00166 {
00167     inherited::build();
00168     build_();
00169 }
00170 
00171 
00172 void RBMTruncExpLayer::makeDeepCopyFromShallowCopy(CopiesMap& copies)
00173 {
00174     inherited::makeDeepCopyFromShallowCopy(copies);
00175 }
00176 
00177 
00178 } // end of namespace PLearn
00179 
00180 
00181 /*
00182   Local Variables:
00183   mode:c++
00184   c-basic-offset:4
00185   c-file-style:"stroustrup"
00186   c-file-offsets:((innamespace . 0)(inline-open . 0))
00187   indent-tabs-mode:nil
00188   fill-column:79
00189   End:
00190 */
00191 // vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:encoding=utf-8:textwidth=79 :
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