opennlp-ml/src/main/java/org/apache/opennlp/ml/model/UniformPrior.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.
 */

package org.apache.opennlp.ml.model;

/**
 * Provide a maximum entropy model with a uniform prior.
 */
public class UniformPrior implements Prior {

  private int numOutcomes;
  private double r;
    
  public void logPrior(double[] dist, int[] context, float[] values) {
    for (int oi=0;oi<numOutcomes;oi++) {
      dist[oi] = r;
    }
  }
  
  public void logPrior(double[] dist, int[] context) {
    logPrior(dist,context,null);
  }

  public void setLabels(String[] outcomeLabels, String[] contextLabels) {
    this.numOutcomes = outcomeLabels.length;
    r = Math.log(1.0/numOutcomes);
  }
}