/**
* 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.hadoop.util;
import org.mortbay.log.Log;
/**
* A Floyd variation of PriorityQueue. For a simple description see:
* http://en.wikipedia.org/wiki/Heapsort#Variations
*
* Floyd variation works better if the following two assumptions hold:
* 1. Key comparisons are expensive
* 2. Key distribution from different input streams are not skewed
* (which means the new key in the heap is expected to be landed
* at the leaf level (which consists of half of all nodes).
*/
public abstract class PriorityQueueFloyd<T> extends PriorityQueue<T> {
@Override
protected void downHeap() {
int i = 1;
T node = heap[i]; // save top node
int j = i << 1; // find smaller child
int k = j + 1;
while (k <= size) {
if (lessThan(heap[k], heap[j])) {
j = k;
}
heap[i] = heap[j];
i = j;
j = i << 1;
k = j + 1;
}
// set node to the leaf and push upHeap
if (j > size) { // i is a leaf node
j = i;
} else { // j is the last leaf node
assert(j == size);
heap[i] = heap[j];
}
heap[j] = node;
upHeap(j);
}
}