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/*
 * Anserini: A Lucene toolkit for reproducible information retrieval research
 *
 * 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.
 */

package io.anserini.ltr;

import java.util.List;

public class VarPooler implements Pooler {
  public float pool(List array) {
    float sum = 0;
    float squareSum = 0;
    for (float v : array) {
      sum += v;
      squareSum += v * v;
    }
    float avg = sum / array.size();
    return (squareSum / array.size() - avg * avg);
  }

  public Pooler clone() {
    return new VarPooler();
  }

  public String getName() {
    return "var";
  }
}