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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.aggregators.matrix;
20  
21  import java.util.ArrayList;
22  
23  /**
24   * The abstract matrix aggregator contains the prefix name of the vector
25   * aggregators that have the values of the rows. It also cashes the names to
26   * avoid creating the same string multiples times.
27   */
28  public abstract class MatrixSumAggregator {
29    /**
30     * The prefix name of the vector aggregators. The aggregator names are created
31     * as (name0, name1, ...).
32     */
33    private String name;
34    /** Cache the names of the columns */
35    private ArrayList<String> names = new ArrayList<String>();
36  
37    /**
38     * Create a new matrix aggregator with the given prefix name for the vector
39     * aggregators.
40     *
41     * @param name the prefix for the row vector aggregators
42     */
43    public MatrixSumAggregator(String name) {
44      this.name = name;
45    }
46  
47    /**
48     * Get the name of the aggreagator of the row with the index specified.
49     *
50     * @param i the row of the matrix
51     * @return the name of the aggregator
52     */
53    protected String getRowAggregatorName(int i) {
54      for (int n = names.size(); n <= i; ++n) {
55        names.add(name + n);
56      }
57      return names.get(i);
58    }
59  }