// Copyright (C) 2003 Samy Bengio (bengio@idiap.ch)
//                
// This file is part of Torch 3.
//
// All rights reserved.
// 
// 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.
// 2. Redistributions in binary form must reproduce the above copyright
//    notice, this list of conditions and the following disclaimer in the
//    documentation and/or other materials provided with the distribution.
// 3. The name of the author may not be used to endorse or promote products
//    derived from this software without specific prior written permission.
// 
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#ifndef SOFT_PLUS_INC
#define SOFT_PLUS_INC

#include "GradientMachine.h"

namespace Torch {

/** SoftPlus layer for #GradientMachine#.
    
    Can be used to constrain the output of a machine to be always positive.
    The number of inputs/outputs is the number of units in the machine.

    Formally speaking, $ouputs[i] = log(1+exp(inputs[i]))$

    @author Samy Bengio (bengio@idiap.ch)
*/
class SoftPlus : public GradientMachine
{
  public:

    /// Create a layer with #n_units# units.
    SoftPlus(int n_units);

    //-----

    virtual void frameForward(int t, real *f_inputs, real *f_outputs);
    virtual void frameBackward(int t, real *f_inputs, real *beta_, real *f_outputs, real *alpha_);
    
    virtual ~SoftPlus();
};

}

#endif