PLearn 0.1
PowVariableVariable.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: PowVariableVariable.cc 3994 2005-08-25 13:35:03Z chapados $
00040  * This file is part of the PLearn library.
00041  ******************************************************* */
00042 
00043 #include "DotProductVariable.h"
00044 #include "IfThenElseVariable.h"
00045 #include "IsAboveThresholdVariable.h"
00046 #include "LogVariable.h"
00047 #include "PowVariableVariable.h"
00048 #include "Var_operators.h"
00049 
00050 namespace PLearn {
00051 using namespace std;
00052 
00053 
00056 /* PowVariableVariable: x^y where x and y are variables but y is scalar 
00057    or it has the same size as x */
00058 
00059 PLEARN_IMPLEMENT_OBJECT(PowVariableVariable,
00060                         "x^y where x and y are variables but y is scalar "
00061                         "or it has the same size as x",
00062                         "NO HELP");
00063 
00064 PowVariableVariable::PowVariableVariable(Variable* input1, Variable* input2)
00065     : inherited(input1, input2, input1->length(), input1->width())
00066 {
00067     build_();
00068 }
00069 
00070 void
00071 PowVariableVariable::build()
00072 {
00073     inherited::build();
00074     build_();
00075 }
00076 
00077 void
00078 PowVariableVariable::build_()
00079 {
00080     if (input1 && input2) {
00081         if(!input2->isScalar() && (input1->length()!=input2->length() || input1->width()!=input2->width()))
00082             PLERROR("IN FunctionPowVariableVariable(Variable* input1, Variable* input2) input1 and input2 must have the same size or input2 must be scalar");
00083     }
00084 }
00085 
00086 void PowVariableVariable::recomputeSize(int& l, int& w) const
00087 {
00088     if (input1) {
00089         l = input1->length();
00090         w = input1->width();
00091     } else
00092         l = w = 0;
00093 }
00094 
00095 
00096 void PowVariableVariable::fprop()
00097 {
00098     if (input2->isScalar())
00099     {
00100         real p = input2->valuedata[0];
00101         for(int i=0; i<nelems(); i++)
00102             if (input1->valuedata[i]>0)
00103                 valuedata[i] = pow(input1->valuedata[i],p);
00104             else
00105                 valuedata[i] = 0;
00106     }
00107     else
00108         for(int i=0; i<nelems(); i++)
00109             if (input1->valuedata[i]>0)
00110                 valuedata[i] = pow(input1->valuedata[i],input2->valuedata[i]);
00111             else
00112                 valuedata[i] = 0;
00113 }
00114 
00115 
00116 void PowVariableVariable::bprop()
00117 {
00118     if (input2->isScalar())
00119     {
00120         real p = input2->valuedata[0];
00121         real& dp = input2->gradientdata[0];
00122         for(int i=0; i<nelems(); i++)
00123         {
00124             if (input1->valuedata[i]>0)
00125             {
00126                 input1->gradientdata[i] += 
00127                     gradientdata[i] * valuedata[i] * p / input1->valuedata[i];
00128                 dp += gradientdata[i] * valuedata[i] * safeflog(input1->valuedata[i]);
00129             }
00130         }
00131     }
00132     else
00133     {
00134         for(int i=0; i<nelems(); i++)
00135         {
00136             if (input1->valuedata[i]>0)
00137             {
00138                 input1->gradientdata[i] += 
00139                     gradientdata[i] * valuedata[i] * input2->valuedata[i] 
00140                     / input1->valuedata[i];
00141                 input2->gradientdata[i] += 
00142                     gradientdata[i] * valuedata[i] * safeflog(input1->valuedata[i]);
00143             }
00144         }
00145     }
00146 }
00147 
00148 
00149 void PowVariableVariable::symbolicBprop()
00150 {
00151     Var gv = g * Var(this);
00152     Var input1zero = (input1<=0.0);
00153     Var zero(length(), width());
00154     input1->accg(ifThenElse(input1zero, zero, gv * input2 / input1));
00155     if (input2->isScalar())
00156         input2->accg(dot(gv,ifThenElse(input1zero, zero, log(input1))));
00157     else
00158         input2->accg(ifThenElse(input1zero, zero, gv * log(input1)));
00159 }
00160 
00161 
00162 
00163 } // end of namespace PLearn
00164 
00165 
00166 /*
00167   Local Variables:
00168   mode:c++
00169   c-basic-offset:4
00170   c-file-style:"stroustrup"
00171   c-file-offsets:((innamespace . 0)(inline-open . 0))
00172   indent-tabs-mode:nil
00173   fill-column:79
00174   End:
00175 */
00176 // vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:encoding=utf-8:textwidth=79 :
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