org.nd4j.linalg.activations.impl.ActivationELU Maven / Gradle / Ivy
package org.nd4j.linalg.activations.impl;
import lombok.EqualsAndHashCode;
import lombok.Getter;
import org.nd4j.linalg.primitives.Pair;
import org.nd4j.linalg.activations.BaseActivationFunction;
import org.nd4j.linalg.api.ndarray.INDArray;
import org.nd4j.linalg.api.ops.impl.transforms.ELU;
import org.nd4j.linalg.api.ops.impl.transforms.gradient.ELUDerivative;
import org.nd4j.linalg.factory.Nd4j;
import org.nd4j.linalg.indexing.BooleanIndexing;
import org.nd4j.linalg.indexing.conditions.Conditions;
/**
* f(x) = alpha * (exp(x) - 1.0); x < 0
* = x ; x>= 0
*
* alpha defaults to 1, if not specified
*/
@EqualsAndHashCode
@Getter
public class ActivationELU extends BaseActivationFunction {
public static final double DEFAULT_ALPHA = 1.0;
private double alpha = DEFAULT_ALPHA;
public ActivationELU() {
this(DEFAULT_ALPHA);
}
public ActivationELU(double alpha) {
this.alpha = alpha;
}
/*
= alpha * (exp(x) - 1.0); x < 0
f(x)
= x ; x >= 0
*/
@Override
public INDArray getActivation(INDArray in, boolean training) {
// no support in ELU native to override alpha
if (this.alpha != 1.00) {
INDArray alphaMultiple = Nd4j.getExecutioner().execAndReturn(new ELU(in.dup()));
alphaMultiple.muli(alpha);
BooleanIndexing.replaceWhere(in, alphaMultiple, Conditions.lessThan(0));
} else {
Nd4j.getExecutioner().execAndReturn(new ELU(in));
}
return in;
}
/*
= alpha * exp(x) ; x < 0
f'(x)
= 1 ; x >= 0
*/
@Override
public Pair backprop(INDArray in, INDArray epsilon) {
// no support in ELU native to override alpha
if (alpha != 1.00) {
INDArray dLdz = Nd4j.getExecutioner().execAndReturn(new ELUDerivative(in.dup()));
dLdz.muli(alpha);
BooleanIndexing.replaceWhere(dLdz, 1, Conditions.equals(alpha));
dLdz.muli(epsilon);
return new Pair<>(dLdz, null);
}
else {
INDArray dLdz = Nd4j.getExecutioner().execAndReturn(new ELUDerivative(in));
dLdz.muli(epsilon);
return new Pair<>(dLdz, null);
}
}
@Override
public String toString() {
return "elu(alpha=" + alpha + ")";
}
}