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);