org.nd4j.linalg.activations.impl.ActivationRReLU Maven / Gradle / Ivy
package org.nd4j.linalg.activations.impl;
import lombok.EqualsAndHashCode;
import lombok.Getter;
import org.apache.commons.math3.util.Pair;
import org.nd4j.linalg.activations.BaseActivationFunction;
import org.nd4j.linalg.api.ndarray.INDArray;
import org.nd4j.linalg.api.ops.impl.transforms.RectifedLinear;
import org.nd4j.linalg.factory.Nd4j;
import org.nd4j.linalg.indexing.BooleanIndexing;
import org.nd4j.linalg.indexing.conditions.Conditions;
import org.nd4j.shade.jackson.annotation.JsonIgnoreProperties;
/**
* f(x) = max(0,x) + alpha * min(0, x)
*
* alpha is drawn from uniform(l,u) during training and is set to l+u/2 during test
* l and u default to 1/8 and 1/3 respectively
*
*
* Empirical Evaluation of Rectified Activations in Convolutional Network
*/
@EqualsAndHashCode
@JsonIgnoreProperties({"alpha"})
@Getter
public class ActivationRReLU extends BaseActivationFunction {
public static final double DEFAULT_L = 1.0 / 8;
public static final double DEFAULT_U = 1.0 / 3;
private double l, u;
private transient INDArray alpha; //don't need to write to json, when streaming
public ActivationRReLU() {
this(DEFAULT_L, DEFAULT_U);
}
public ActivationRReLU(double l, double u) {
if (l > u) {
throw new IllegalArgumentException("Cannot have lower value (" + l + ") greater than upper (" + u + ")");
}
this.l = l;
this.u = u;
}
@Override
public INDArray getActivation(INDArray in, boolean training) {
if (training) {
this.alpha = Nd4j.rand(in.shape(), l, u, Nd4j.getRandom());
INDArray inTimesAlpha = in.mul(alpha);
BooleanIndexing.replaceWhere(in, inTimesAlpha, Conditions.lessThan(0));
} else {
this.alpha = null;
double a = 0.5 * (l + u);
return Nd4j.getExecutioner().execAndReturn(new RectifedLinear(in, a));
}
return in;
}
@Override
public Pair backprop(INDArray in, INDArray epsilon) {
INDArray dLdz = Nd4j.ones(in.shape());
BooleanIndexing.replaceWhere(dLdz, alpha, Conditions.lessThanOrEqual(0.0));
dLdz.muli(epsilon);
return new Pair<>(dLdz, null);
}
@Override
public String toString() {
return "rrelu(l=" + l + ", u=" + u + ")";
}
}