001/* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017package org.apache.commons.math3.util; 018 019import java.io.Serializable; 020 021import org.apache.commons.math3.exception.MathIllegalArgumentException; 022 023 024/** 025 * A mid point strategy based on the average of begin and end indices. 026 * @since 3.4 027 */ 028public class CentralPivotingStrategy implements PivotingStrategyInterface, Serializable { 029 030 /** Serializable UID. */ 031 private static final long serialVersionUID = 20140713L; 032 033 /** 034 * {@inheritDoc} 035 * This in particular picks a average of begin and end indices 036 * @return The index corresponding to a simple average of 037 * the first and the last element indices of the array slice 038 * @throws MathIllegalArgumentException when indices exceeds range 039 */ 040 public int pivotIndex(final double[] work, final int begin, final int end) 041 throws MathIllegalArgumentException { 042 MathArrays.verifyValues(work, begin, end-begin); 043 return begin + (end - begin)/2; 044 } 045 046}