Source code

001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *   http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing,
013 * software distributed under the License is distributed on an
014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 * KIND, either express or implied.  See the License for the
016 * specific language governing permissions and limitations
017 * under the License.
018 */
019package org.apache.reef.examples.group.bgd.loss;
020
021import javax.inject.Inject;
022
023/**
024 * Logistic {@link LossFunction}.
025 */
026public final class LogisticLossFunction implements LossFunction {
027
028  /**
029   * Trivial constructor.
030   */
031  @Inject
032  public LogisticLossFunction() {
033  }
034
035  @Override
036  public double computeLoss(final double y, final double f) {
037    final double predictedTimesLabel = y * f;
038    return Math.log(1 + Math.exp(-predictedTimesLabel));
039  }
040
041  @Override
042  public double computeGradient(final double y, final double f) {
043    final double predictedTimesLabel = y * f;
044    return -y / (1 + Math.exp(predictedTimesLabel));
045  }
046
047  @Override
048  public String toString() {
049    return "LogisticLossFunction{}";
050  }
051}
052
053