lib: optimize priority queue

Author: gurgunday

lib/internal/priority_queue.js

@@ -47,20 +47,28 @@ module.exports = class PriorityQueue {
  const setPosition = this.#setPosition;
  const heap = this.#heap;
  const size = this.#size;
+ const hsize = size >> 1;
  const item = heap[pos];
 
- while (pos * 2 <= size) {
- let childIndex = pos * 2 + 1;
- if (childIndex > size || compare(heap[pos * 2], heap[childIndex]) < 0)
- childIndex = pos * 2;
- const child = heap[childIndex];
- if (compare(item, child) <= 0)
- break;
+ while (pos <= hsize) {
+ let child = pos << 1;
+ const nextChild = child + 1;
+ let childItem = heap[child];
+
+ if (nextChild <= size && compare(heap[nextChild], childItem) < 0) {
+ child = nextChild;
+ childItem = heap[nextChild];
+ }
+
+ if (compare(item, childItem) <= 0) break;
+
  if (setPosition !== undefined)
- setPosition(child, pos);
- heap[pos] = child;
- pos = childIndex;
+ setPosition(childItem, pos);
+
+ heap[pos] = childItem;
+ pos = child;
  }
+
  heap[pos] = item;
  if (setPosition !== undefined)
  setPosition(item, pos);
@@ -73,27 +81,31 @@ module.exports = class PriorityQueue {
  const item = heap[pos];
 
  while (pos > 1) {
- const parent = heap[pos / 2 | 0];
- if (compare(parent, item) <= 0)
+ const parent = pos >> 1;
+ const parentItem = heap[parent];
+ if (compare(parentItem, item) <= 0)
  break;
- heap[pos] = parent;
+ heap[pos] = parentItem;
  if (setPosition !== undefined)
- setPosition(parent, pos);
- pos = pos / 2 | 0;
+ setPosition(parentItem, pos);
+ pos = parent;
  }
+
  heap[pos] = item;
  if (setPosition !== undefined)
  setPosition(item, pos);
  }
 
  removeAt(pos) {
+ if (pos > this.#size) return;
+
  const heap = this.#heap;
  const size = --this.#size;
  heap[pos] = heap[size + 1];
  heap[size + 1] = undefined;
 
  if (size > 0 && pos <= size) {
- if (pos > 1 && this.#compare(heap[pos / 2 | 0], heap[pos]) > 0)
+ if (pos > 1 && this.#compare(heap[pos >> 1], heap[pos]) > 0)
  this.percolateUp(pos);
  else
  this.percolateDown(pos);