Source code

001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *   http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing,
013 * software distributed under the License is distributed on an
014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 * KIND, either express or implied.  See the License for the
016 * specific language governing permissions and limitations
017 * under the License.
018 */
019package org.apache.reef.io.network.group.impl.utils;
020
021import java.util.ArrayList;
022import java.util.List;
023
024/**
025 * Utility class for ScatterSender.
026 */
027public final class ScatterHelper {
028
029  /**
030   * Should not be instantiated.
031   */
032  private ScatterHelper() {
033  }
034
035  /**
036   * Uniformly distribute a number of elements across a number of Tasks and return a list of counts.
037   * If uniform distribution is impossible, then some Tasks will receive one
038   * more element than others. The sequence of the number of elements for each
039   * Task is non-increasing.
040   *
041   * @param elementCount number of elements to distribute
042   * @param taskCount number of Tasks that receive elements
043   * @return list of counts specifying how many elements each Task should receive
044   */
045  public static List<Integer> getUniformCounts(final int elementCount, final int taskCount) {
046    final int quotient = elementCount / taskCount;
047    final int remainder = elementCount % taskCount;
048
049    final List<Integer> retList = new ArrayList<>();
050    for (int taskIndex = 0; taskIndex < taskCount; taskIndex++) {
051      if (taskIndex < remainder) {
052        retList.add(quotient + 1);
053      } else {
054        retList.add(quotient);
055      }
056    }
057    return retList;
058  }
059}