PLearn 0.1
LogSoftmaxVariable.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 
00009 // Redistribution and use in source and binary forms, with or without
00010 // modification, are permitted provided that the following conditions are met:
00011 // 
00012 //  1. Redistributions of source code must retain the above copyright
00013 //     notice, this list of conditions and the following disclaimer.
00014 // 
00015 //  2. Redistributions in binary form must reproduce the above copyright
00016 //     notice, this list of conditions and the following disclaimer in the
00017 //     documentation and/or other materials provided with the distribution.
00018 // 
00019 //  3. The name of the authors may not be used to endorse or promote
00020 //     products derived from this software without specific prior written
00021 //     permission.
00022 // 
00023 // THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
00024 // IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
00025 // OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN
00026 // NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
00027 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
00028 // TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
00029 // PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
00030 // LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
00031 // NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
00032 // SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
00033 // 
00034 // This file is part of the PLearn library. For more information on the PLearn
00035 // library, go to the PLearn Web site at www.plearn.org
00036 
00037 
00038 /* *******************************************************      
00039  * $Id: LogSoftmaxVariable.cc 8847 2008-04-21 20:49:49Z tihocan $
00040  * This file is part of the PLearn library.
00041  ******************************************************* */
00042 
00043 #include "LogSoftmaxVariable.h"
00044 
00045 namespace PLearn {
00046 using namespace std;
00047 
00048 
00051 PLEARN_IMPLEMENT_OBJECT(
00052         LogSoftmaxVariable,
00053         "Compute the logarithm of the softmax of its input.",
00054         "This is more stable than combinining a softmax and a logarithm."
00055 );
00056 
00058 // LogSoftmaxVariable //
00060 LogSoftmaxVariable::LogSoftmaxVariable(Variable* input, bool call_build_):
00061     inherited(input, input->length(), input->width(), call_build_)
00062 {
00063     if (call_build_)
00064         build_();
00065 }
00066 
00068 // build //
00070 void LogSoftmaxVariable::build()
00071 {
00072     inherited::build();
00073     build_();
00074 }
00075 
00077 // build_ //
00079 void LogSoftmaxVariable::build_()
00080 {
00081     // Nothing to do here.
00082 }
00083 
00084 void LogSoftmaxVariable::recomputeSize(int& l, int& w) const
00085 {
00086     if (input) {
00087         l = input->length();
00088         w = input->width();
00089     } else
00090         l = w = 0;
00091 }
00092 
00093 void
00094 LogSoftmaxVariable::fprop()
00095 {
00096     log_softmax(input->value, value);
00097 }
00098 
00099 
00100 void
00101 LogSoftmaxVariable::bprop()
00102 {
00103     for (int i = 0; i < input->nelems(); ++i) {
00104         real sum = 0.;
00105         for (int k = 0; k < nelems(); ++k)
00106             sum += gradientdata[k];
00107         input->gradientdata[i] += gradientdata[i] - sum * safeexp(valuedata[i]);
00108     }
00109 }
00110 
00111 
00112 void
00113 LogSoftmaxVariable::bbprop()
00114 {
00115     PLERROR("LogSofmaxVariable::bbprop() not implemented");
00116 }
00117 
00118 
00119 void
00120 LogSoftmaxVariable::symbolicBprop()
00121 {
00122     PLERROR("LogSofmaxVariable::symbolicBprop() not implemented");
00123 }
00124 
00125 
00126 
00127 } // end of namespace PLearn
00128 
00129 
00130 /*
00131   Local Variables:
00132   mode:c++
00133   c-basic-offset:4
00134   c-file-style:"stroustrup"
00135   c-file-offsets:((innamespace . 0)(inline-open . 0))
00136   indent-tabs-mode:nil
00137   fill-column:79
00138   End:
00139 */
00140 // vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:encoding=utf-8:textwidth=79 :
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