Max2Variable.cc

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// -*- C++ -*-

// PLearn (A C++ Machine Learning Library)
// Copyright (C) 1998 Pascal Vincent
// Copyright (C) 1999-2002 Pascal Vincent, Yoshua Bengio, Rejean Ducharme and University of Montreal
// Copyright (C) 2001-2002 Nicolas Chapados, Ichiro Takeuchi, Jean-Sebastien Senecal
// Copyright (C) 2002 Xiangdong Wang, Christian Dorion

// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
// 
//  1. Redistributions of source code must retain the above copyright
//     notice, this list of conditions and the following disclaimer.
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/* *******************************************************      
   * $Id: Max2Variable.cc,v 1.6 2004/04/27 15:58:16 morinf Exp $
   * This file is part of the PLearn library.
   ******************************************************* */

#include "Max2Variable.h"
#include "Var_operators.h"

namespace PLearn {
using namespace std;


PLEARN_IMPLEMENT_OBJECT(Max2Variable,
                        "Elementwise max over 2 elements: max(v1,v2)[i] = max(v1[i],v2[i]) "
                        "with same dimensions as the input vectors",
                        "NO HELP");

Max2Variable::Max2Variable(Variable* input1, Variable* input2)
  : inherited(input1, input2, input1->length(), input1->width())
{
    build_();
}

void
Max2Variable::build()
{
    inherited::build();
    build_();
}

void
Max2Variable::build_()
{
    if (input1 && input2) {
        if (input1->length() != input2->length()  ||  input1->width() != input2->width())
            PLERROR("IN Max2Variable input1 and input2 must have the same size");
    }
}


void Max2Variable::recomputeSize(int& l, int& w) const
{
    if (input1) {
        l = input1->length();
        w = input1->width();
    } else
        l = w = 0;
}

void Max2Variable::fprop()
{
  int n=input1->value.length();
  real* v1=input1->value.data();
  real* v2=input2->value.data();
  real* v=value.data();
  for (int i=0;i<n;i++)
    v[i] = std::max(v1[i],v2[i]);
}


void Max2Variable::bprop()
{
  int n=input1->value.length();
  real* v1=input1->value.data();
  real* v2=input2->value.data();
  real* grad1=input1->gradient.data();
  real* grad2=input2->gradient.data();
  real* grad=gradient.data();
  for (int i=0;i<n;i++)
  {
    if (v2[i]<v1[i])
      grad1[i] += grad[i];
    if (v1[i]<v2[i])
      grad2[i] += grad[i];
  }
}


void Max2Variable::symbolicBprop()
{
  input1->accg((input2<input1)*g);
  input2->accg((input1<input2)*g);
}



} // end of namespace PLearn

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