PLearn 0.1
CosKernel.cc
Go to the documentation of this file.
00001 // -*- C++ -*-
00002 
00003 // PLearn (A C++ Machine Learning Library)
00004 // Copyright (C) 2007 Jerome Louradour
00005 
00006 // Redistribution and use in source and binary forms, with or without
00007 // modification, are permitted provided that the following conditions are met:
00008 // 
00009 //  1. Redistributions of source code must retain the above copyright
00010 //     notice, this list of conditions and the following disclaimer.
00011 // 
00012 //  2. Redistributions in binary form must reproduce the above copyright
00013 //     notice, this list of conditions and the following disclaimer in the
00014 //     documentation and/or other materials provided with the distribution.
00015 // 
00016 //  3. The name of the authors may not be used to endorse or promote
00017 //     products derived from this software without specific prior written
00018 //     permission.
00019 // 
00020 // THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
00021 // IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
00022 // OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN
00023 // NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
00024 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
00025 // TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
00026 // PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
00027 // LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
00028 // NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
00029 // SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
00030 // 
00031 // This file is part of the PLearn library. For more information on the PLearn
00032 // library, go to the PLearn Web site at www.plearn.org
00033 
00034 
00035 /* *******************************************************      
00036  * $Id: CosKernel.cc 7675 2007-06-29 19:50:49Z tihocan $
00037  * This file is part of the PLearn library.
00038  ******************************************************* */
00039 
00040 #include "CosKernel.h"
00041 
00042 namespace PLearn {
00043 using namespace std;
00044 
00045 
00046 PLEARN_IMPLEMENT_OBJECT(
00047     CosKernel,
00048     "Implements a distance based on a cosinus.",
00049     "Output k(x,y)=(0.5 - 0.5*cos(x,y)) (between 0 and 1)\n");
00050 
00052 // CosKernel //
00054 CosKernel::CosKernel()
00055 {
00056     n=2.0;
00057     optimized=false;
00058     pow_distance=false;
00059     ignore_missing=false;
00060 }
00061 
00063 // declareOptions //
00065 void CosKernel::declareOptions(OptionList& ol)
00066 {
00067     inherited::declareOptions(ol);
00068 
00069     redeclareOption(ol, "n", &CosKernel::n, OptionBase::nosave, 
00070                   "Obsolete option for cosinus kernel.");
00071 
00072     redeclareOption(ol, "pow_distance", &CosKernel::pow_distance, OptionBase::nosave, 
00073                   "Obsolete option for cosinus kernel.");
00074 
00075     redeclareOption(ol, "optimized", &CosKernel::optimized, OptionBase::nosave, 
00076                   "Obsolete option for cosinus kernel.");
00077 
00078     redeclareOption(ol, "ignore_missing", &CosKernel::ignore_missing, OptionBase::nosave, 
00079                   "Obsolete option for cosinus kernel.");
00080 }
00081 
00083 // evaluate //
00085 real CosKernel::evaluate(const Vec& x1, const Vec& x2) const {
00086     if (ignore_missing && !pow_distance)
00087         PLERROR("In CosKernel::evaluate(int i, int j) - 'ignore_missing' "
00088                 "implemented only if pow_distance is set");
00089     static real cosinus;
00090     cosinus = dot(x1, x2) / ( norm(x1) * norm(x2) );
00091     return (1.-cosinus)*.5;
00092 }
00093 
00095 // evaluate_i_j //
00097 real CosKernel::evaluate_i_j(int i, int j) const {
00098     static real cosinus;
00099     if (i == j)
00100         // The case 'i == j' can cause precision issues because of the optimized
00101         // formula below. Thus we make sure we always return 0.
00102         return 0;
00103     cosinus = data->dot(i, j, data_inputsize) / sqrt(squarednorms[i] * squarednorms[j]);
00104     return (1.-cosinus)*.5;
00105 }
00106 
00107 } // end of namespace PLearn
00108 
00109 
00110 /*
00111   Local Variables:
00112   mode:c++
00113   c-basic-offset:4
00114   c-file-style:"stroustrup"
00115   c-file-offsets:((innamespace . 0)(inline-open . 0))
00116   indent-tabs-mode:nil
00117   fill-column:79
00118   End:
00119 */
00120 // vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:encoding=utf-8:textwidth=79 :
 All Classes Namespaces Files Functions Variables Typedefs Enumerations Enumerator Friends Defines