/*
* Encog(tm) Core v3.4 - Java Version
* http://www.heatonresearch.com/encog/
* https://github.com/encog/encog-java-core
* Copyright 2008-2016 Heaton Research, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* For more information on Heaton Research copyrights, licenses
* and trademarks visit:
* http://www.heatonresearch.com/copyright
*/
package org.encog.engine.network.activation;
import org.encog.ml.factory.MLActivationFactory;
import org.encog.util.obj.ActivationUtil;
/**
* A ramp activation function. This function has a high and low threshold. If
* the high threshold is exceeded a fixed value is returned. Likewise, if the
* low value is exceeded another fixed value is returned.
*
*/
public class ActivationRamp implements ActivationFunction {
/**
* The ramp high threshold parameter.
*/
public static final int PARAM_RAMP_HIGH_THRESHOLD = 0;
/**
* The ramp low threshold parameter.
*/
public static final int PARAM_RAMP_LOW_THRESHOLD = 1;
/**
* The ramp high parameter.
*/
public static final int PARAM_RAMP_HIGH = 2;
/**
* The ramp low parameter.
*/
public static final int PARAM_RAMP_LOW = 3;
/**
* The serial ID.
*/
private static final long serialVersionUID = 6336245112244386279L;
/**
* The parameters.
*/
private final double[] params;
/**
* Default constructor.
*/
public ActivationRamp() {
this(1, 0, 1, 0);
}
/**
* Construct a ramp activation function.
*
* @param thresholdHigh
* The high threshold value.
* @param thresholdLow
* The low threshold value.
* @param high
* The high value, replaced if the high threshold is exceeded.
* @param low
* The low value, replaced if the low threshold is exceeded.
*/
public ActivationRamp(final double thresholdHigh,
final double thresholdLow, final double high, final double low) {
this.params = new double[4];
this.params[ActivationRamp.PARAM_RAMP_HIGH_THRESHOLD] = thresholdHigh;
this.params[ActivationRamp.PARAM_RAMP_LOW_THRESHOLD] = thresholdLow;
this.params[ActivationRamp.PARAM_RAMP_HIGH] = high;
this.params[ActivationRamp.PARAM_RAMP_LOW] = low;
}
/**
* {@inheritDoc}
*/
@Override
public final void activationFunction(final double[] x, final int start,
final int size) {
final double slope = (this.params[ActivationRamp.PARAM_RAMP_HIGH_THRESHOLD] - this.params[ActivationRamp.PARAM_RAMP_LOW_THRESHOLD])
/ (this.params[ActivationRamp.PARAM_RAMP_HIGH] - this.params[ActivationRamp.PARAM_RAMP_LOW]);
for (int i = start; i < start + size; i++) {
if (x[i] < this.params[ActivationRamp.PARAM_RAMP_LOW_THRESHOLD]) {
x[i] = this.params[ActivationRamp.PARAM_RAMP_LOW];
} else if (x[i] > this.params[ActivationRamp.PARAM_RAMP_HIGH_THRESHOLD]) {
x[i] = this.params[ActivationRamp.PARAM_RAMP_HIGH];
} else {
x[i] = (slope * x[i]);
}
}
}
/**
* Clone the object.
*
* @return The cloned object.
*/
@Override
public final ActivationFunction clone() {
return new ActivationRamp(
this.params[ActivationRamp.PARAM_RAMP_HIGH_THRESHOLD],
this.params[ActivationRamp.PARAM_RAMP_LOW_THRESHOLD],
this.params[ActivationRamp.PARAM_RAMP_HIGH],
this.params[ActivationRamp.PARAM_RAMP_LOW]);
}
/**
* {@inheritDoc}
*/
@Override
public final double derivativeFunction(final double b, final double a) {
return 1.0;
}
/**
* @return the high
*/
public final double getHigh() {
return this.params[ActivationRamp.PARAM_RAMP_HIGH];
}
/**
* @return the low
*/
public final double getLow() {
return this.params[ActivationRamp.PARAM_RAMP_LOW];
}
/**
* {@inheritDoc}
*/
@Override
public final String[] getParamNames() {
final String[] result = { "thresholdHigh", "thresholdLow", "high",
"low" };
return result;
}
/**
* {@inheritDoc}
*/
@Override
public final double[] getParams() {
return this.params;
}
/**
* @return the thresholdHigh
*/
public final double getThresholdHigh() {
return this.params[ActivationRamp.PARAM_RAMP_HIGH_THRESHOLD];
}
/**
* @return the thresholdLow
*/
public final double getThresholdLow() {
return this.params[ActivationRamp.PARAM_RAMP_LOW_THRESHOLD];
}
/**
* @return True, as this function does have a derivative.
*/
@Override
public final boolean hasDerivative() {
return true;
}
/**
* Set the high value.
*
* @param d
* The high value.
*/
public final void setHigh(final double d) {
setParam(ActivationRamp.PARAM_RAMP_HIGH, d);
}
/**
* Set the low value.
*
* @param d
* The low value.
*/
public final void setLow(final double d) {
setParam(ActivationRamp.PARAM_RAMP_LOW, d);
}
/**
* {@inheritDoc}
*/
@Override
public final void setParam(final int index, final double value) {
this.params[index] = value;
}
/**
* Set the threshold high.
*
* @param d
* The threshold high.
*/
public final void setThresholdHigh(final double d) {
setParam(ActivationRamp.PARAM_RAMP_HIGH_THRESHOLD, d);
}
/**
* Set the threshold low.
*
* @param d
* The threshold low.
*/
public final void setThresholdLow(final double d) {
setParam(ActivationRamp.PARAM_RAMP_LOW_THRESHOLD, d);
}
/**
* {@inheritDoc}
*/
@Override
public String getFactoryCode() {
return ActivationUtil.generateActivationFactory(MLActivationFactory.AF_RAMP, this);
}
@Override
public String getLabel() {
return "ramp";
}
}