PLearn 0.1
SoftSlopeVariable.h
Go to the documentation of this file.
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: SoftSlopeVariable.h 3994 2005-08-25 13:35:03Z chapados $
00040  * This file is part of the PLearn library.
00041  ******************************************************* */
00042 
00043 #ifndef SoftSlopeVariable_INC
00044 #define SoftSlopeVariable_INC
00045 
00046 #include "NaryVariable.h"
00047 #include "SigmoidVariable.h"
00048 #include "Var_operators.h"
00049 
00050 namespace PLearn {
00051 using namespace std;
00052 
00053 
00054 // as smoothness-->infty this becomes the linear by part function that
00055 // is 0 in [-infty,left], linear in [left,right], and 1 in [right,infty].
00056 // For finite smoothness, it is a smoother function, always with value in the interval [0,1].
00057 // It is always monotonically increasing wrt x (positive derivative in x).
00058 class SoftSlopeVariable: public NaryVariable
00059 {
00060     typedef NaryVariable inherited;
00061 
00062 protected:
00063     bool tabulated;
00064 
00065 public:
00067     SoftSlopeVariable() {}
00068     SoftSlopeVariable(Variable* x, Variable* smoothness, Variable* left, Variable* right, bool tabulated=true);
00069 
00070     PLEARN_DECLARE_OBJECT(SoftSlopeVariable);
00071     static void declareOptions(OptionList &ol);
00072 
00073     virtual void recomputeSize(int& l, int& w) const;
00074     virtual void fprop();
00075     virtual void bprop();
00076     virtual void symbolicBprop();
00077 };
00078 
00079 DECLARE_OBJECT_PTR(SoftSlopeVariable);
00080 
00081 inline Var soft_slope(Var x, Var smoothness, Var left, Var right)
00082 { return new SoftSlopeVariable(x,smoothness,left,right); }
00083 
00084 // derivative of soft_slope wrt x
00085 inline Var d_soft_slope(Var x, Var smoothness, Var left, Var right)
00086 {
00087     return (-sigmoid(-smoothness*(x-left))+sigmoid(-smoothness*(x-right)))/(right-left);
00088 }
00089 
00090 // limit of soft_slope when smoothness-->0
00091 inline Var soft_slope_limit(Var x, Var smoothness, Var left, Var right)
00092 {
00093     int l=0; 
00094     int w=0;
00095     if (x->length()>l) l=x->length();
00096     if (x->width()>w) w=x->width();
00097     if (smoothness->length()>l) l=smoothness->length();
00098     if (smoothness->width()>w) w=smoothness->width();
00099     if (left->length()>l) l=left->length();
00100     if (left->width()>w) w=left->width();
00101     if (right->length()>l) l=right->length();
00102     if (right->width()>w) w=right->width();
00103     if (x->length()>l && l!=x->length()) PLERROR("soft_slope_limit: Each argument should have the same size or size 1");
00104     if (x->width()>w && w!=x->width()) PLERROR("soft_slope_limit: Each argument should have the same size or size 1");
00105     if (smoothness->length()>l && l!=smoothness->length())  PLERROR("soft_slope_limit: Each argument should have the same size or size 1");
00106     if (smoothness->width()>w && w!=smoothness->width())  PLERROR("soft_slope_limit: Each argument should have the same size or size 1");
00107     if (left->length()>l && l!=left->length())  PLERROR("soft_slope_limit: Each argument should have the same size or size 1");
00108     if (left->width()>w && w!=left->width())  PLERROR("soft_slope_limit: Each argument should have the same size or size 1");
00109     if (right->length()>l && l!=right->length())  PLERROR("soft_slope_limit: Each argument should have the same size or size 1");
00110     if (right->width()>w && w!=right->width())  PLERROR("soft_slope_limit: Each argument should have the same size or size 1");
00111     Var res(l,w);
00112     res->value.fill(0.5);
00113     return res;
00114 }
00115 
00116 } // end of namespace PLearn
00117 
00118 #endif 
00119 
00120 
00121 /*
00122   Local Variables:
00123   mode:c++
00124   c-basic-offset:4
00125   c-file-style:"stroustrup"
00126   c-file-offsets:((innamespace . 0)(inline-open . 0))
00127   indent-tabs-mode:nil
00128   fill-column:79
00129   End:
00130 */
00131 // 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