/* * 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.commons.math3.util; import java.io.Serializable; import org.apache.commons.math3.exception.MathIllegalArgumentException; /** * A mid point strategy based on the average of begin and end indices. * @since 3.4 */ public class CentralPivotingStrategy implements PivotingStrategyInterface, Serializable { /** Serializable UID. */ private static final long serialVersionUID = 20140713L; /** * {@inheritDoc} * This in particular picks a average of begin and end indices * @return The index corresponding to a simple average of * the first and the last element indices of the array slice * @throws MathIllegalArgumentException when indices exceeds range */ public int pivotIndex(final double[] work, final int begin, final int end) throws MathIllegalArgumentException { MathArrays.verifyValues(work, begin, end-begin); return begin + (end - begin)/2; } }