org.apache.solr.util.LongPriorityQueue Maven / Gradle / Ivy
Show all versions of solr-core Show documentation
/*
* 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.solr.util;
import java.util.Arrays;
/**
* A native long priority queue.
*
* @lucene.internal
*/
public class LongPriorityQueue {
protected int size; // number of elements currently in the queue
protected int currentCapacity; // number of elements the queue can hold w/o expanding
protected int maxSize; // max number of elements allowed in the queue
protected long[] heap;
protected final long sentinel; // represents a null return value
public LongPriorityQueue(int initialSize, int maxSize, long sentinel) {
this.maxSize = maxSize;
this.sentinel = sentinel;
initialize(initialSize);
}
protected void initialize(int sz) {
int heapSize;
if (0 == sz)
// We allocate 1 extra to avoid if statement in top()
heapSize = 2;
else {
// NOTE: we add +1 because all access to heap is
// 1-based not 0-based. heap[0] is unused.
heapSize = Math.max(sz, sz + 1); // handle overflow
}
heap = new long[heapSize];
currentCapacity = sz;
}
public int getCurrentCapacity() {
return currentCapacity;
}
public void resize(int sz) {
int heapSize;
if (sz > maxSize) {
maxSize = sz;
}
if (0 == sz)
// We allocate 1 extra to avoid if statement in top()
heapSize = 2;
else {
heapSize = Math.max(sz, sz + 1); // handle overflow
}
heap = Arrays.copyOf(heap, heapSize);
currentCapacity = sz;
}
/**
* Adds an object to a PriorityQueue in log(size) time. If one tries to add more objects than
* maxSize from initialize an {@link ArrayIndexOutOfBoundsException} is thrown.
*
* @return the new 'top' element in the queue.
*/
public long add(long element) {
if (size >= currentCapacity) {
int newSize = Math.min(currentCapacity << 1, maxSize);
if (newSize < currentCapacity) newSize = Integer.MAX_VALUE; // handle overflow
resize(newSize);
}
size++;
heap[size] = element;
upHeap();
return heap[1];
}
/**
* Adds an object to a PriorityQueue in log(size) time. If one tries to add more objects than the
* current capacity, an {@link ArrayIndexOutOfBoundsException} is thrown.
*/
public void addNoCheck(long element) {
++size;
heap[size] = element;
upHeap();
}
/**
* Adds an object to a PriorityQueue in log(size) time. It returns the smallest object (if any)
* that was dropped off the heap because it was full, or the sentinel value.
*
* This can be the given parameter (in case it is smaller than the full heap's minimum, and
* couldn't be added), or another object that was previously the smallest value in the heap and
* now has been replaced by a larger one, or null if the queue wasn't yet full with maxSize
* elements.
*/
public long insertWithOverflow(long element) {
if (size < maxSize) {
add(element);
return sentinel;
} else if (element > heap[1]) {
long ret = heap[1];
heap[1] = element;
updateTop();
return ret;
} else {
return element;
}
}
/**
* inserts the element and returns true if this element caused another element to be dropped from
* the queue.
*/
public boolean insert(long element) {
if (size < maxSize) {
add(element);
return false;
} else if (element > heap[1]) {
// long ret = heap[1];
heap[1] = element;
updateTop();
return true;
} else {
return false;
}
}
/** Returns the least element of the PriorityQueue in constant time. */
public long top() {
return heap[1];
}
/**
* Removes and returns the least element of the PriorityQueue in log(size) time. Only valid if
* size() > 0.
*/
public long pop() {
long result = heap[1]; // save first value
heap[1] = heap[size]; // move last to first
size--;
downHeap(); // adjust heap
return result;
}
/**
* Should be called when the Object at top changes values.
*
* @return the new 'top' element.
*/
public long updateTop() {
downHeap();
return heap[1];
}
/** Returns the number of elements currently stored in the PriorityQueue. */
public int size() {
return size;
}
/**
* Returns the array used to hold the heap, with the smallest item at array[1] and the last (but
* not necessarily largest) at array[size()]. This is *not* fully sorted.
*/
public long[] getInternalArray() {
return heap;
}
/**
* Pops the smallest n items from the heap, placing them in the internal array at arr[size]
* through arr[size-(n-1)] with the smallest (first element popped) being at arr[size]. The
* internal array is returned.
*/
public long[] sort(int n) {
while (--n >= 0) {
long result = heap[1]; // save first value
heap[1] = heap[size]; // move last to first
heap[size] = result; // place it last
size--;
downHeap(); // adjust heap
}
return heap;
}
/** Removes all entries from the PriorityQueue. */
public void clear() {
size = 0;
}
private void upHeap() {
int i = size;
long node = heap[i]; // save bottom node
int j = i >>> 1;
while (j > 0 && node < heap[j]) {
heap[i] = heap[j]; // shift parents down
i = j;
j = j >>> 1;
}
heap[i] = node; // install saved node
}
private void downHeap() {
int i = 1;
long node = heap[i]; // save top node
int j = i << 1; // find smaller child
int k = j + 1;
if (k <= size && heap[k] < heap[j]) {
j = k;
}
while (j <= size && heap[j] < node) {
heap[i] = heap[j]; // shift up child
i = j;
j = i << 1;
k = j + 1;
if (k <= size && heap[k] < heap[j]) {
j = k;
}
}
heap[i] = node; // install saved node
}
}