PLearn 0.1
SquareRootVariable.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: SquareRootVariable.cc 3994 2005-08-25 13:35:03Z chapados $
00040  * This file is part of the PLearn library.
00041  ******************************************************* */
00042 
00043 #include "SquareRootVariable.h"
00044 
00045 namespace PLearn {
00046 using namespace std;
00047 
00048 
00049 
00052 PLEARN_IMPLEMENT_OBJECT(SquareRootVariable,
00053                         "ONE LINE DESCR",
00054                         "NO HELP");
00055 
00056 SquareRootVariable::SquareRootVariable(Variable* input)
00057     : inherited(input, input->length(), input->width())
00058 {}
00059 
00060 void SquareRootVariable::recomputeSize(int& l, int& w) const
00061 {
00062     if (input) {
00063         l = input->length();
00064         w = input->width();
00065     } else
00066         l = w = 0;
00067 }
00068 
00069 void SquareRootVariable::fprop()
00070 {
00071     int n=nelems();
00072     for(int i=0; i<n; i++)
00073         valuedata[i] = sqrt(input->valuedata[i]);
00074 }
00075 
00076 
00077 // dC/dx = dC/dy * 1/2 * 1/sqrt(x)
00078 void SquareRootVariable::bprop()
00079 {
00080     if (rValue.length()==0) resizeRValue();
00081     int n=nelems();
00082     for(int i=0; i<n; i++)
00083     {
00084         input->gradientdata[i] += 0.5/sqrt(input->valuedata[i]) * gradientdata[i];
00085         rvaluedata[i] = 2*input->valuedata[i]*input->rvaluedata[i];
00086     }
00087 }
00088 
00092 // void SquareRootVariable::bbprop()
00093 // {
00094 //   if (input->diaghessian.length()==0)
00095 //     input->resizeDiagHessian();
00096 //   int n=nelems();
00097 //   for(int i=0; i<n; i++)
00098 //   {
00099 //     real input_i = input->valuedata[i];
00100 //     input->diaghessiandata[i] += 1/(4*input_i) * diaghessiandata[i]
00101 //                                  + (-0.25) * pow( i/sqrt(input_i), 3 ) * gradientdata[i];
00102 //   }
00103 // }
00104 
00105 
00106 } // end of namespace PLearn
00107 
00108 
00109 /*
00110   Local Variables:
00111   mode:c++
00112   c-basic-offset:4
00113   c-file-style:"stroustrup"
00114   c-file-offsets:((innamespace . 0)(inline-open . 0))
00115   indent-tabs-mode:nil
00116   fill-column:79
00117   End:
00118 */
00119 // vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:encoding=utf-8:textwidth=79 :
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