PLearn 0.1
MaxVariable.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: MaxVariable.cc 6438 2006-11-16 15:01:40Z chapados $
00040  * This file is part of the PLearn library.
00041  ******************************************************* */
00042 
00043 #include "ArgmaxVariable.h"
00044 #include "ElementAtPositionVariable.h"
00045 #include "MaxVariable.h"
00046 
00047 namespace PLearn {
00048 using namespace std;
00049 
00050 
00053 PLEARN_IMPLEMENT_OBJECT(
00054     MaxVariable,
00055     "Variable which returns the maximum value of its (single) input",
00056     "This Variable always has a size of 1 element:\n"
00057     "\n"
00058     "   value(0,0) = max_i input[i]\n"
00059     "\n"
00060     "where input[i] is the i-th element of its input variable\n"
00061     "(dimensionality does not matter; it's viewed as a long vector).");
00062 
00063 MaxVariable::MaxVariable(Variable* input)
00064     : inherited(input, 1, 1)
00065 {}
00066 
00067 void MaxVariable::recomputeSize(int& l, int& w) const
00068 { l=1; w=1; }
00069 
00070 void MaxVariable::fprop()
00071 {
00072     real maxval = input->valuedata[0];
00073     for(int i=1; i<input->nelems(); i++)
00074     {
00075         real val = input->valuedata[i];
00076         if(val>maxval)
00077             maxval = val;
00078     }
00079     valuedata[0] = maxval;
00080 }
00081 
00082 
00083 void MaxVariable::bprop()
00084 {
00085     real maxval = valuedata[0];
00086     for(int i=0; i<input->nelems(); i++)
00087     {
00088         if(input->valuedata[i]==maxval)
00089             input->gradientdata[i] += gradientdata[0];
00090     }
00091 }
00092 
00093 
00094 void MaxVariable::symbolicBprop()
00095 {
00096     input->accg(new ElementAtPositionVariable(g, argmax(input), input->length(), input->width()));
00097 }
00098 
00099 } // end of namespace PLearn
00100 
00101 
00102 /*
00103   Local Variables:
00104   mode:c++
00105   c-basic-offset:4
00106   c-file-style:"stroustrup"
00107   c-file-offsets:((innamespace . 0)(inline-open . 0))
00108   indent-tabs-mode:nil
00109   fill-column:79
00110   End:
00111 */
00112 // vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:encoding=utf-8:textwidth=79 :
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