Day 74：通用BP神经网络 (1. 集中管理激活函数)
代码：
package dl;
/**
* Activator.
*/
public class Activator {
/**
* Arc tan.
*/
public final char ARC_TAN = 'a';
/**
* Elu.
*/
public final char ELU = 'e';
/**
* Gelu.
*/
public final char GELU = 'g';
/**
* Hard logistic.
*/
public final char HARD_LOGISTIC = 'h';
/**
* Identity.
*/
public final char IDENTITY = 'i';
/**
* Leaky relu, also known as parametric relu.
*/
public final char LEAKY_RELU = 'l';
/**
* Relu.
*/
public final char RELU = 'r';
/**
* Soft sign.
*/
public final char SOFT_SIGN = 'o';
/**
* Sigmoid.
*/
public final char SIGMOID = 's';
/**
* Tanh.
*/
public final char TANH = 't';
/**
* Soft plus.
*/
public final char SOFT_PLUS = 'u';
/**
* Swish.
*/
public final char SWISH = 'w';
/**
* The activator.
*/
private char activator;
/**
* Alpha for elu.
*/
double alpha;
/**
* Beta for leaky relu.
*/
double beta;
/**
* Gamma for leaky relu.
*/
double gamma;
/**
*********************
* The first constructor.
*
* @param paraActivator
* The activator.
*********************
*/
public Activator(char paraActivator) {
activator = paraActivator;
}// Of the first constructor
/**
*********************
* Setter.
*********************
*/
public void setActivator(char paraActivator) {
activator = paraActivator;
}// Of setActivator
/**
*********************
* Getter.
*********************
*/
public char getActivator() {
return activator;
}// Of getActivator
/**
*********************
* Setter.
*********************
*/
void setAlpha(double paraAlpha) {
alpha = paraAlpha;
}// Of setAlpha
/**
*********************
* Setter.
*********************
*/
void setBeta(double paraBeta) {
beta = paraBeta;
}// Of setBeta
/**
*********************
* Setter.
*********************
*/
void setGamma(double paraGamma) {
gamma = paraGamma;
}// Of setGamma
/**
*********************
* Activate according to the activation function.
*********************
*/
public double activate(double paraValue) {
double resultValue = 0;
switch (activator) {
case ARC_TAN:
resultValue = Math.atan(paraValue);
break;
case ELU:
if (paraValue >= 0) {
resultValue = paraValue;
} else {
resultValue = alpha * (Math.exp(paraValue) - 1);
} // Of if
break;
// case GELU:
// resultValue = ?;
// break;
// case HARD_LOGISTIC:
// resultValue = ?;
// break;
case IDENTITY:
resultValue = paraValue;
break;
case LEAKY_RELU:
if (paraValue >= 0) {
resultValue = paraValue;
} else {
resultValue = alpha * paraValue;
} // Of if
break;
case SOFT_SIGN:
if (paraValue >= 0) {
resultValue = paraValue / (1 + paraValue);
} else {
resultValue = paraValue / (1 - paraValue);
} // Of if
break;
case SOFT_PLUS:
resultValue = Math.log(1 + Math.exp(paraValue));
break;
case RELU:
if (paraValue >= 0) {
resultValue = paraValue;
} else {
resultValue = 0;
} // Of if
break;
case SIGMOID:
resultValue = 1 / (1 + Math.exp(-paraValue));
break;
case TANH:
resultValue = 2 / (1 + Math.exp(-2 * paraValue)) - 1;
break;
// case SWISH:
// resultValue = ?;
// break;
default:
System.out.println("Unsupported activator: " + activator);
System.exit(0);
}// Of switch
return resultValue;
}// Of activate
/**
*********************
* Derive according to the activation function. Some use x while others use
* f(x).
*
* @param paraValue
* The original value x.
* @param paraActivatedValue
* f(x).
*********************
*/
public double derive(double paraValue, double paraActivatedValue) {
double resultValue = 0;
switch (activator) {
case ARC_TAN:
resultValue = 1 / (paraValue * paraValue + 1);
break;
case ELU:
if (paraValue >= 0) {
resultValue = 1;
} else {
resultValue = alpha * (Math.exp(paraValue) - 1) + alpha;
} // Of if
break;
// case GELU:
// resultValue = ?;
// break;
// case HARD_LOGISTIC:
// resultValue = ?;
// break;
case IDENTITY:
resultValue = 1;
break;
case LEAKY_RELU:
if (paraValue >= 0) {
resultValue = 1;
} else {
resultValue = alpha;
} // Of if
break;
case SOFT_SIGN:
if (paraValue >= 0) {
resultValue = 1 / (1 + paraValue) / (1 + paraValue);
} else {
resultValue = 1 / (1 - paraValue) / (1 - paraValue);
} // Of if
break;
case SOFT_PLUS:
resultValue = 1 / (1 + Math.exp(-paraValue));
break;
case RELU: // Updated
if (paraValue >= 0) {
resultValue = 1;
} else {
resultValue = 0;
} // Of if
break;
case SIGMOID: // Updated
resultValue = paraActivatedValue * (1 - paraActivatedValue);
break;
case TANH: // Updated
resultValue = 1 - paraActivatedValue * paraActivatedValue;
break;
// case SWISH:
// resultValue = ?;
// break;
default:
System.out.println("Unsupported activator: " + activator);
System.exit(0);
}// Of switch
return resultValue;
}// Of derive
/**
*********************
* Overrides the method claimed in Object.
*********************
*/
public String toString() {
String resultString = "Activator with function '" + activator + "'";
resultString += "\r\n alpha = " + alpha + ", beta = " + beta + ", gamma = " + gamma;
return resultString;
}// Of toString
/**
********************
* Test the class.
********************
*/
public static void main(String[] args) {
Activator tempActivator = new Activator('s');
double tempValue = 0.6;
double tempNewValue;
tempNewValue = tempActivator.activate(tempValue);
System.out.println("After activation: " + tempNewValue);
tempNewValue = tempActivator.derive(tempValue, tempNewValue);
System.out.println("After derive: " + tempNewValue);
}// Of main
}// Of class Activator
结果：
