org.nd4j.linalg.activations.impl.ActivationRationalTanh 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.RationalTanh;
import org.nd4j.linalg.api.ops.impl.transforms.RationalTanhDerivative;
import org.nd4j.linalg.factory.Nd4j;
/**
* Rational tanh approximation
* From https://arxiv.org/pdf/1508.01292v3
*
* f(x) = 1.7159 * tanh(2x/3)
* where tanh is approximated as follows,
* tanh(y) ~ sgn(y) * { 1 - 1/(1+|y|+y^2+1.41645*y^4)}
*
* Underlying implementation is in native code
*/
@EqualsAndHashCode
@Getter
public class ActivationRationalTanh extends BaseActivationFunction {
@Override
public INDArray getActivation(INDArray in, boolean training) {
Nd4j.getExecutioner().execAndReturn(new RationalTanh(in));
return in;
}
@Override
public Pair backprop(INDArray in, INDArray epsilon) {
INDArray dLdz = Nd4j.getExecutioner().execAndReturn(new RationalTanhDerivative(in));
dLdz.muli(epsilon);
return new Pair<>(dLdz, null);
}
@Override
public String toString() {
return "rationaltanh";
}
}