PLearn 0.1
PLogPVariable.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: PLogPVariable.cc 3994 2005-08-25 13:35:03Z chapados $
00040  * This file is part of the PLearn library.
00041  ******************************************************* */
00042 
00043 #include "LogVariable.h"
00044 #include "PLogPVariable.h"
00045 #include "Var_operators.h"
00046 
00047 namespace PLearn {
00048 using namespace std;
00049 
00050 
00053 PLEARN_IMPLEMENT_OBJECT(PLogPVariable,
00054                         "Returns the elementwise x*log(x) in a (hopefully!) numerically stable way",
00055                         "NO HELP");
00056 
00057 PLogPVariable::PLogPVariable(Variable* input)
00058     : inherited(input, input->length(), input->width())
00059 {}
00060 
00061 
00062 void PLogPVariable::recomputeSize(int& l, int& w) const
00063 {
00064     if (input) {
00065         l = input->length();
00066         w = input->width();
00067     } else
00068         l = w = 0;
00069 }
00070 
00071 void PLogPVariable::fprop()
00072 {
00073     for(int i=0; i<nelems(); i++)
00074     {
00075         real p = input->valuedata[i];
00076         if(p<1e-10)
00077             p = 1e-10;
00078         valuedata[i] = p*safeflog(p);
00079     }
00080 }
00081 
00082 
00083 void PLogPVariable::bprop()
00084 {
00085     for(int i=0; i<nelems(); i++)
00086     {
00087         real p = input->valuedata[i];
00088         if(p<1e-10)
00089             p = 1e-10;
00090         input->gradientdata[i] += gradientdata[i]*(1.0+safeflog(p));
00091     }
00092 }
00093 
00094 
00095 void PLogPVariable::symbolicBprop()
00096 {
00097     input->accg(g * (1.+log(input)));
00098 }
00099 
00100 
00101 
00102 } // end of namespace PLearn
00103 
00104 
00105 /*
00106   Local Variables:
00107   mode:c++
00108   c-basic-offset:4
00109   c-file-style:"stroustrup"
00110   c-file-offsets:((innamespace . 0)(inline-open . 0))
00111   indent-tabs-mode:nil
00112   fill-column:79
00113   End:
00114 */
00115 // vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:encoding=utf-8:textwidth=79 :
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