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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one
3    * or more contributor license agreements.  See the NOTICE file
4    * distributed with this work for additional information
5    * regarding copyright ownership.  The ASF licenses this file
6    * to you under the Apache License, Version 2.0 (the
7    * "License"); you may not use this file except in compliance
8    * with the License.  You may obtain a copy of the License at
9    *
10   *     http://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing, software
13   * distributed under the License is distributed on an "AS IS" BASIS,
14   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15   * See the License for the specific language governing permissions and
16   * limitations under the License.
17   */
18  
19  package org.apache.giraph.utils;
20  
21  import org.apache.hadoop.io.DoubleWritable;
22  
23  import java.util.Iterator;
24  
25  /**
26   * A helper class for math related operations with writables
27   */
28  public class MathUtils {
29  
30    /**
31     * Utility classes cannot be instantiated
32     */
33    private MathUtils() {
34    }
35  
36    /**
37     * Sums up a sequence of double values
38     * @param values double values
39     * @return sum of double values
40     */
41    public static double sum(Iterable<DoubleWritable> values) {
42      return sum(values.iterator());
43    }
44  
45    /**
46     * Sums up a sequence of double values
47     * @param values double values
48     * @return sum of double values
49     */
50    public static double sum(Iterator<DoubleWritable> values) {
51      double sum = 0;
52      while (values.hasNext()) {
53        sum += values.next().get();
54      }
55      return sum;
56    }
57  }