org.nd4j.linalg.schedule.SigmoidSchedule Maven / Gradle / Ivy
/*******************************************************************************
* Copyright (c) 2015-2018 Skymind, Inc.
*
* This program and the accompanying materials are made available under the
* terms of the Apache License, Version 2.0 which is available at
* https://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.
*
* SPDX-License-Identifier: Apache-2.0
******************************************************************************/
package org.nd4j.linalg.schedule;
import lombok.Data;
import org.nd4j.shade.jackson.annotation.JsonProperty;
/**
* Sigmoid decay schedule, with 3 parameters: initial value, gamma and stepSize.
* value(i) = initialValue * 1.0 / (1 + exp(-gamma * (iter - stepSize)))
* where i is the iteration or epoch (depending on the setting)
*
* @author Alex Black
*/
@Data
public class SigmoidSchedule implements ISchedule {
private final ScheduleType scheduleType;
private final double initialValue;
private final double gamma;
private final int stepSize;
public SigmoidSchedule(@JsonProperty("scheduleType") ScheduleType scheduleType,
@JsonProperty("initialValue") double initialValue,
@JsonProperty("gamma") double gamma,
@JsonProperty("stepSize") int stepSize){
this.scheduleType = scheduleType;
this.initialValue = initialValue;
this.gamma = gamma;
this.stepSize = stepSize;
}
@Override
public double valueAt(int iteration, int epoch) {
int i = (scheduleType == ScheduleType.ITERATION ? iteration : epoch);
return initialValue / (1.0 + Math.exp(-gamma * (i - stepSize)));
}
@Override
public ISchedule clone() {
return new SigmoidSchedule(scheduleType, initialValue, gamma, stepSize);
}
}