org.elasticsearch.common.util.BigLongArray Maven / Gradle / Ivy
/*
* Licensed to ElasticSearch and Shay Banon under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. ElasticSearch 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.elasticsearch.common.util;
import java.util.Locale;
/**
* A GC friendly long[].
* Allocating large arrays (that are not short-lived) generate fragmentation
* in old-gen space. This breaks such large long array into fixed size pages
* to avoid that problem.
*/
public class BigLongArray {
private static final int DEFAULT_PAGE_SIZE = 4096;
private final long[][] pages;
public final int size;
private final int pageSize;
private final int pageCount;
public BigLongArray(int size) {
this(size, DEFAULT_PAGE_SIZE);
}
public BigLongArray(int size, int pageSize) {
this.size = size;
this.pageSize = pageSize;
int lastPageSize = size % pageSize;
int fullPageCount = size / pageSize;
pageCount = fullPageCount + (lastPageSize == 0 ? 0 : 1);
pages = new long[pageCount][];
for (int i = 0; i < fullPageCount; ++i)
pages[i] = new long[pageSize];
if (lastPageSize != 0)
pages[pages.length - 1] = new long[lastPageSize];
}
public void set(int idx, long value) {
if (idx < 0 || idx > size)
throw new IndexOutOfBoundsException(String.format(Locale.ROOT, "%d is not whithin [0, %d)", idx, size));
int page = idx / pageSize;
int pageIdx = idx % pageSize;
pages[page][pageIdx] = value;
}
public long get(int idx) {
if (idx < 0 || idx > size)
throw new IndexOutOfBoundsException(String.format(Locale.ROOT, "%d is not whithin [0, %d)", idx, size));
int page = idx / pageSize;
int pageIdx = idx % pageSize;
return pages[page][pageIdx];
}
}