激活函数实现--2 Sigmoid函数实现

1.Sigmoid函数的定义

2.Sigmoid函数的导数

3.SIGMOID激活的实现过程

<span style="font-size:24px;">#ifndef SIGMOID_H
#define SIGMOID_H

#include "abstractactivationfunction.h"

/**
* @brief The Sigmoid class used to calculate the sigmoid activation function.
*
* @author sheng
* @date  2014-07-18
* @version 0.1
*
* @history
*     <author>       <date>         <version>        <description>
*      sheng       2014-07-18          0.1         build the class
*
*/
class Sigmoid : public AbstractActivationFunction
{
public:
Sigmoid();

cv::Mat Activating(const cv::Mat& InputMat);
cv::Mat Derivating(const cv::Mat& InputMat);
};

#endif // SIGMOID_H
</span>

<span style="font-size:24px;">#include "sigmoid.h"

#include <iostream>

/**
* @brief The default constructor.
*
* @author sheng
* @version 0.1
* @date 2014-07-18
*
* @history
*     <author>       <date>         <version>        <description>
*      sheng       2014-07-18          0.1         build the function
*
*
*/
Sigmoid::Sigmoid()
{
}

/**
* @brief Calculating the sigmoid of the inputmat.
* @param InputMat  The input mat
* @return the result of sigmoid(inputmat), whose size is the same of the
*         InputMat.
*
*
* @author sheng
* @version 0.1
* @date 2014-07-18
*
* @history
*     <author>       <date>         <version>        <description>
*      sheng       2014-07-18          0.1         build the function
*
*
*
*/

cv::Mat Sigmoid::Activating(const cv::Mat& InputMat)
{
// convert the mat to be float
cv::Mat FloatInput = ConvertToFloatMat(InputMat);

// calculate the exp(-x)
cv::Mat TmpExp;
cv::exp(-FloatInput, TmpExp);

// calculate the sigmoid
cv::Mat ResultMat = 1.0 / (1.0 + TmpExp);

return ResultMat;
}

/**
* @brief Calculating the derivating of the sigmoid function.
* @param InputMat The input mat.
* @return The result of the derivative of the sigmoid function, whose size is
*         the same of the input mat.
*
* @author sheng
* @version 0.1
* @date 2014-07-18
*
* @history
*     <author>       <date>         <version>        <description>
*      sheng       2014-07-18          0.1         build the function
*
*
*/
cv::Mat Sigmoid::Derivating(const cv::Mat &InputMat)
{
// calculating the sigmoid
cv::Mat TmpMat = Activating(InputMat);

// calculating the derivate of sigmoid function
cv::Mat ResultMat = TmpMat.mul(1.0 - TmpMat);

return ResultMat;
}</span>