spark HashMapGrowthStrategy 源码
spark HashMapGrowthStrategy 代码
文件路径：/core/src/main/java/org/apache/spark/unsafe/map/HashMapGrowthStrategy.java
/*
* 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.spark.unsafe.map;
import org.apache.spark.unsafe.array.ByteArrayMethods;
/**
* Interface that defines how we can grow the size of a hash map when it is over a threshold.
*/
public interface HashMapGrowthStrategy {
int nextCapacity(int currentCapacity);
/**
* Double the size of the hash map every time.
*/
HashMapGrowthStrategy DOUBLING = new Doubling();
class Doubling implements HashMapGrowthStrategy {
private static final int ARRAY_MAX = ByteArrayMethods.MAX_ROUNDED_ARRAY_LENGTH;
@Override
public int nextCapacity(int currentCapacity) {
assert (currentCapacity > 0);
int doubleCapacity = currentCapacity * 2;
// Guard against overflow
return (doubleCapacity > 0 && doubleCapacity <= ARRAY_MAX) ? doubleCapacity : ARRAY_MAX;
}
}
}
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