/*

  * 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.giraph.aggregators.matrix;

 import java.util.ArrayList;

 /**

  * The abstract matrix aggregator contains the prefix name of the vector

  * aggregators that have the values of the rows. It also cashes the names to

  * avoid creating the same string multiples times.

  */

 public abstract class MatrixSumAggregator {

   /**

    * The prefix name of the vector aggregators. The aggregator names are created

    * as (name0, name1, ...).

    */

   private String name;

   /** Cache the names of the columns */

   private ArrayList<String> names = new ArrayList<>();

   /**

    * Create a new matrix aggregator with the given prefix name for the vector

    * aggregators.

    *

    * @param name the prefix for the row vector aggregators

    */

   public MatrixSumAggregator(String name) {

     this.name = name;

   }

   /**

    * Get the name of the aggreagator of the row with the index specified.

    *

    * @param i the row of the matrix

    * @return the name of the aggregator

    */

   protected String getRowAggregatorName(int i) {

     for (int n = names.size(); n <= i; ++n) {

       names.add(name + n);

     }

     return names.get(i);

   }

 }