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Improve MinHeap implementation
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Migrated to a new algorithm that does not go beyond the array, thus de-optimization of this piece of code is not happening
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Tom910 committed Apr 1, 2021
1 parent 64983aa commit 5fb47c2
Showing 1 changed file with 44 additions and 45 deletions.
89 changes: 44 additions & 45 deletions packages/scheduler/src/SchedulerMinHeap.js
Original file line number Diff line number Diff line change
Expand Up @@ -20,72 +20,71 @@ export function push(heap: Heap, node: Node): void {
}

export function peek(heap: Heap): Node | null {
const first = heap[0];
return first === undefined ? null : first;
return heap.length === 0 ? null : heap[0];
}

export function pop(heap: Heap): Node | null {
const first = heap[0];
if (first !== undefined) {
const last = heap.pop();
if (last !== first) {
heap[0] = last;
siftDown(heap, last, 0);
}
return first;
} else {
if (heap.length === 0) {
return null;
}
const first = heap[0];

const last = heap.pop();

if (last !== first) {
heap[0] = last;
siftDown(heap, last, 0);
}

return first;
}

function siftUp(heap, node, i) {
let index = i;
while (true) {

while (index > 0) {
const parentIndex = (index - 1) >>> 1;
const parent = heap[parentIndex];
if (parent !== undefined && compare(parent, node) > 0) {
// The parent is larger. Swap positions.
heap[parentIndex] = node;
heap[index] = parent;
index = parentIndex;
} else {
// The parent is smaller. Exit.
return;

if (compare(parent, node) < 0) {
break;
}
swap(heap, parentIndex, index);
index = parentIndex;
}
}

function siftDown(heap, node, i) {
let index = i;
const length = heap.length;
while (index < length) {
const leftIndex = (index + 1) * 2 - 1;
const left = heap[leftIndex];
const rightIndex = leftIndex + 1;
const right = heap[rightIndex];

// If the left or right node is smaller, swap with the smaller of those.
if (left !== undefined && compare(left, node) < 0) {
if (right !== undefined && compare(right, left) < 0) {
heap[index] = right;
heap[rightIndex] = node;
index = rightIndex;
} else {
heap[index] = left;
heap[leftIndex] = node;
index = leftIndex;
}
} else if (right !== undefined && compare(right, node) < 0) {
heap[index] = right;
heap[rightIndex] = node;
index = rightIndex;
} else {
// Neither child is smaller. Exit.
return;
const halfLength = heap.length >>> 1;

while (index < halfLength) {
let bestIndex = index * 2 + 1;
const rightIndex = index * 2 + 2;

// If the right node is smaller, swap with the smaller of those.
if (
heap.length > rightIndex &&
compare(heap[rightIndex], heap[bestIndex]) < 0
) {
bestIndex = rightIndex;
}

if (compare(node, heap[bestIndex]) < 0) {
break;
}

swap(heap, bestIndex, index);
index = bestIndex;
}
}

function swap(heap, left, right) {
const item = heap[left];
heap[left] = heap[right];
heap[right] = item;
}

function compare(a, b) {
// Compare sort index first, then task id.
const diff = a.sortIndex - b.sortIndex;
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