PLearn 0.1
InterValuesVariable.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: InterValuesVariable.cc 3994 2005-08-25 13:35:03Z chapados $
00040  * This file is part of the PLearn library.
00041  ******************************************************* */
00042 
00043 #include "ConcatRowsVariable.h"
00044 #include "InterValuesVariable.h"
00045 //#include "Var_operators.h"
00046 //#include "Var_utils.h"
00047 
00048 namespace PLearn {
00049 using namespace std;
00050 
00051 
00054 // if values = [x1,x2,...,x10], the resulting variable is 
00055 // [(x1+x2)/2,(x2+x3)/2, ... (x9+x10)/2]
00056 PLEARN_IMPLEMENT_OBJECT(InterValuesVariable,
00057                         "if values = [x1,x2,...,x10], the resulting variable is [(x1+x2)/2,(x2+x3)/2, ... (x9+x10)/2]",
00058                         "NO HELP");
00059 
00060 InterValuesVariable::InterValuesVariable(Variable* values) 
00061     : inherited(values,values->length()-1,1) 
00062 {
00063     build_();
00064 }
00065 
00066 void
00067 InterValuesVariable::build()
00068 {
00069     inherited::build();
00070     build_();
00071 }
00072 
00073 void
00074 InterValuesVariable::build_()
00075 {
00076     if(input && !input->isColumnVec())
00077         PLERROR("In InterValuesVariable: input must be a column vector (single column matrix)");
00078 }
00079 
00080 
00081 void InterValuesVariable::recomputeSize(int& l, int& w) const
00082 {
00083     if (input)
00084         l = input->length() - 1;
00085     else
00086         l = 0;
00087     w=1;
00088 }
00089 
00090 
00091 void InterValuesVariable::fprop()
00092 {
00093     real prev_x = input->valuedata[0];
00094     for (int i=0;i<nelems();i++)
00095     {
00096         real next_x = input->valuedata[i+1];
00097         valuedata[i] = 0.5 * (prev_x + next_x);
00098         prev_x = next_x;
00099     }
00100 }
00101 
00102 
00103 void InterValuesVariable::bprop()
00104 {
00105     real* prev_dx = &input->gradientdata[0];
00106     for (int i=0;i<nelems();i++)
00107     {
00108         real* next_dx = &input->gradientdata[i+1];
00109         *prev_dx += 0.5 * gradientdata[i];
00110         *next_dx += 0.5 * gradientdata[i];
00111         prev_dx = next_dx;
00112     }
00113 }
00114 
00115 
00116 void InterValuesVariable::symbolicBprop()
00117 {
00118     Var zero(1);
00119     Var g1 = new InterValuesVariable(vconcat(zero & g & (VarArray)zero));
00120 
00121     input->accg(g1);
00122 }
00123 
00124 
00125 
00126 } // end of namespace PLearn
00127 
00128 
00129 /*
00130   Local Variables:
00131   mode:c++
00132   c-basic-offset:4
00133   c-file-style:"stroustrup"
00134   c-file-offsets:((innamespace . 0)(inline-open . 0))
00135   indent-tabs-mode:nil
00136   fill-column:79
00137   End:
00138 */
00139 // vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:encoding=utf-8:textwidth=79 :
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