PLearn 0.1
ClassMarginCostFunction.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: ClassMarginCostFunction.cc 3994 2005-08-25 13:35:03Z chapados $
00040  * This file is part of the PLearn library.
00041  ******************************************************* */
00042 
00043 #include "ClassMarginCostFunction.h"
00044 
00045 namespace PLearn {
00046 using namespace std;
00047 
00048 
00049 PLEARN_IMPLEMENT_OBJECT(ClassMarginCostFunction, "ONE LINE DESCR", "NO HELP");
00050 
00051 real ClassMarginCostFunction::evaluate(const Vec& output, const Vec& target) const
00052 {
00053     real margin;
00054     if (output.length()==1)
00055     {
00056         real out = output[0];
00057         if (output_is_positive)
00058             out = 2*out-1;
00059         margin = binary_target_is_01 ? out*(target[0]-0.5)*4.0 : out*target[0];
00060     }
00061     else // we assume output gives a score for each class
00062     {
00063         int trueclass;
00064         if (target.length()==1)
00065         {
00066             trueclass = int(target[0]);
00067             if (!binary_target_is_01)
00068                 trueclass = (trueclass+1)/2;
00069         }
00070         else
00071             trueclass = argmax(target);
00072     
00073         real trueclass_score = output[trueclass];
00074         output[trueclass] = -FLT_MAX;
00075         real otherclass_score = max(output);
00076         output[trueclass] = trueclass_score;
00077         margin = trueclass_score-otherclass_score;
00078     }
00079     return -margin;
00080 }
00081 
00082 void ClassMarginCostFunction::declareOptions(OptionList &ol)
00083 {
00084     declareOption(ol, "binary_target_is_01", &ClassMarginCostFunction::binary_target_is_01, OptionBase::buildoption, "");
00085     declareOption(ol, "output_is_positive", &ClassMarginCostFunction::output_is_positive, OptionBase::buildoption, "");
00086     inherited::declareOptions(ol);
00087 }
00088 
00089 
00090 
00091 } // end of namespace PLearn
00092 
00093 
00094 /*
00095   Local Variables:
00096   mode:c++
00097   c-basic-offset:4
00098   c-file-style:"stroustrup"
00099   c-file-offsets:((innamespace . 0)(inline-open . 0))
00100   indent-tabs-mode:nil
00101   fill-column:79
00102   End:
00103 */
00104 // vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:encoding=utf-8:textwidth=79 :
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