PLearn 0.1
ArgminOfVariable.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: ArgminOfVariable.cc 6861 2007-04-09 19:04:15Z saintmlx $
00040  * This file is part of the PLearn library.
00041  ******************************************************* */
00042 
00043 #include "ArgminOfVariable.h"
00044 
00045 namespace PLearn {
00046 using namespace std;
00047 
00048 
00050 /* returns the value of v within the_values_of_v that gives the lowest
00051    value of a scalar expression (which may depend on inputs). */
00052 ArgminOfVariable::ArgminOfVariable(Variable* the_v,
00053                                    Variable* the_expression,
00054                                    Variable* the_values_of_v,
00055                                    const VarArray& the_inputs)
00056     :NaryVariable(the_inputs,1,1), inputs(the_inputs), expression(the_expression),
00057      values_of_v(the_values_of_v), v(the_v)
00058 {
00059     if (!v->isScalar() || !values_of_v->isVec())
00060         PLERROR("ArgminOfVariable currently implemented only for a scalar v and a vector values_of_v");
00061     vv_path = propagationPath(inputs,values_of_v);
00062     e_path = propagationPath(inputs& (VarArray)v, expression);
00063     v_path = propagationPath(v, expression);
00064 }
00065 
00066 
00067 PLEARN_IMPLEMENT_OBJECT(ArgminOfVariable, "ONE LINE DESCR", "NO HELP");
00068 
00069 void ArgminOfVariable::recomputeSize(int& l, int& w) const
00070 { l=1; w=1; }
00071 
00072 
00073 void ArgminOfVariable::makeDeepCopyFromShallowCopy(CopiesMap& copies)
00074 {
00075     inherited::makeDeepCopyFromShallowCopy(copies);
00076     deepCopyField(inputs, copies);
00077     deepCopyField(expression, copies);
00078     deepCopyField(values_of_v, copies);
00079     deepCopyField(v, copies);
00080     deepCopyField(vv_path, copies);
00081     deepCopyField(e_path, copies);
00082     deepCopyField(v_path, copies);
00083 }
00084 
00085 
00086 
00087 void ArgminOfVariable::fprop()
00088 {
00089     vv_path.fprop(); // compute influence of inputs on values_of_v
00090     real min_value_of_expression = FLT_MAX;
00091     real argmin_value_of_v = values_of_v->value[0];
00092     for (int i=0;i<values_of_v->nelems();i++)
00093     {
00094         v->value[0] = values_of_v->value[i];
00095         if (i==0)
00096             e_path.fprop(); // compute influence of v and inputs on expression
00097         else
00098             v_path.fprop(); // otherwise, keep influence of inputs fixed
00099         real e = expression->value[0];
00100         if (e<min_value_of_expression)
00101         {
00102             min_value_of_expression = e;
00103             argmin_value_of_v = v->value[0];
00104             index_of_argmin = i;
00105         }
00106     }
00107     value[0] = argmin_value_of_v;
00108 }
00109 
00110 
00111 void ArgminOfVariable::bprop()
00112 {
00113     vv_path.clearGradient();
00114     values_of_v->gradientdata[index_of_argmin] = gradientdata[0];
00115     vv_path.bprop();
00116 }
00117 
00118 
00119 
00120 } // end of namespace PLearn
00121 
00122 
00123 /*
00124   Local Variables:
00125   mode:c++
00126   c-basic-offset:4
00127   c-file-style:"stroustrup"
00128   c-file-offsets:((innamespace . 0)(inline-open . 0))
00129   indent-tabs-mode:nil
00130   fill-column:79
00131   End:
00132 */
00133 // vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:encoding=utf-8:textwidth=79 :
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