Package org.apache.lucene.util

Class TernaryLongHeap

java.lang.Object
org.apache.lucene.util.TernaryLongHeap
public final class TernaryLongHeap extends Object
A ternary min heap that stores longs; a primitive priority queue that like all priority queues maintains a partial ordering of its elements such that the least element can always be found in constant time. Put()'s and pop()'s require log_3(size). This heap provides unbounded growth via push(long), and bounded-size insertion based on its nominal initial capacity via insertWithOverflow(long). The heap is a min heap, meaning that the top element is the lowest value of the heap. TernaryLongHeap implements 3-ary heap.
NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.

  • Constructor Summary

    Constructors
    Constructor
    Description
    TernaryLongHeap(int initialCapacity)
    Create an empty priority queue of the configured initial size.
    TernaryLongHeap(int size, long initialValue)
    Constructs a heap with specified size and initializes all elements with the given value.

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    clear()
    Removes all entries from the PriorityQueue.
    long
    get(int i)
    Return the element at the ith location in the heap array.
    boolean
    insertWithOverflow(long value)
    Adds a value to an TernaryLongHeap in log(size) time.
    long
    pop()
    Removes and returns the least element of the PriorityQueue in log(size) time.
    long
    push(long element)
    Adds a value in log(size) time.
    void
    pushAll(TernaryLongHeap other)
     
    int
    size()
    Returns the number of elements currently stored in the PriorityQueue.
    long
    top()
    Returns the least element of the TernaryLongHeap in constant time.
    long
    updateTop(long value)
    Replace the top of the pq with newTop.

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Constructor Details

    • TernaryLongHeap

      public TernaryLongHeap(int size, long initialValue)
      Constructs a heap with specified size and initializes all elements with the given value.
      Parameters:
      size - the number of elements to initialize in the heap.
      initialValue - the value to fill the heap with.

    • TernaryLongHeap

      public TernaryLongHeap(int initialCapacity)
      Create an empty priority queue of the configured initial size.
      Parameters:
      initialCapacity - the initial capacity of the heap

  • Method Details

    • push

      public long push(long element)
      Adds a value in log(size) time. Grows unbounded as needed to accommodate new values.
      Returns:
      the new 'top' element in the queue.

    • insertWithOverflow

      public boolean insertWithOverflow(long value)
      Adds a value to an TernaryLongHeap in log(size) time. If the number of values would exceed the heap's initialCapacity, the least value is discarded.
      Returns:
      whether the value was added (unless the heap is full, or the new value is less than the top value)

    • top

      public long top()
      Returns the least element of the TernaryLongHeap in constant time. It is up to the caller to verify that the heap is not empty; no checking is done, and if no elements have been added, 0 is returned.

    • pop

      public long pop()
      Removes and returns the least element of the PriorityQueue in log(size) time.
      Throws:
      IllegalStateException - if the TernaryLongHeap is empty.

    • updateTop

      public long updateTop(long value)
      Replace the top of the pq with newTop. Should be called when the top value changes. Still log(n) worst case, but it's at least twice as fast to 
       pq.updateTop(value);

      instead of 

       pq.pop();
 pq.push(value);

      Calling this method on an empty TernaryLongHeap has no visible effect.

      Parameters:
      value - the new element that is less than the current top.
      Returns:
      the new 'top' element after shuffling the heap.

    • size

      public int size()
      Returns the number of elements currently stored in the PriorityQueue.

    • clear

      public void clear()
      Removes all entries from the PriorityQueue.

    • pushAll

      public void pushAll(TernaryLongHeap other)

    • get

      public long get(int i)
      Return the element at the ith location in the heap array. Use for iterating over elements when the order doesn't matter. Note that the valid arguments range from [1, size].