org.apache.lucene.util.InPlaceMergeSorter Maven / Gradle / Ivy
package org.apache.lucene.util;
/*
* 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.
*/
/** {@link Sorter} implementation based on the merge-sort algorithm that merges
* in place (no extra memory will be allocated). Small arrays are sorted with
* insertion sort.
* @lucene.internal */
public abstract class InPlaceMergeSorter extends Sorter {
/** Create a new {@link InPlaceMergeSorter} */
public InPlaceMergeSorter() {}
@Override
public final void sort(int from, int to) {
checkRange(from, to);
mergeSort(from, to);
}
void mergeSort(int from, int to) {
if (to - from < THRESHOLD) {
insertionSort(from, to);
} else {
final int mid = (from + to) >>> 1;
mergeSort(from, mid);
mergeSort(mid, to);
mergeInPlace(from, mid, to);
}
}
}