奇妙なJavaScript / Node.jsのパフォーマンスの問題

現在、私は非常に奇妙なパフォーマンスの問題に苦しんでいます。SlowHeapにかかる平均は1448.623msですが、FastHeapに必要なのは550.425msだけです。私はそれを何度も見てきましたが、2つの違いは、最初の要素が_arrの先頭に「未定義」の要素を使用し、2番目の要素が使用しないことだけです。ただし、どちらも同じ操作を実行します。下のコードで確認したこと。

この問題に光を当てることができる人はいますか？

let slowHeapOperationCount = 0
let fastHeapOperationCount = 0

let slowHeapExchanged = []
let fastHeapExchanged = []

function SlowHeap(cmp = (a, b) => a > b ? 1 : a < b ? -1 : 0) {
    this.cmp = cmp
    this._arr = [undefined]
    this.size = 0
}
function FastHeap(cmp = (a, b) => a > b ? 1 : a < b ? -1 : 0) {
    this.cmp = cmp
    this._arr = []
    this.size = 0
}

SlowHeap.prototype.bubbleUp = function (cmp, _arr, val) {
    let idxNr = this.size, parentIdxNr = idxNr >> 1
    while (idxNr > 0 && cmp(_arr[parentIdxNr], val) > 0) {
        slowHeapExchanged.push([_arr[parentIdxNr], val])

        _arr[idxNr] = _arr[parentIdxNr]
        _arr[parentIdxNr] = val

        idxNr = parentIdxNr
        parentIdxNr = idxNr >> 1

        slowHeapOperationCount++
    }
}
FastHeap.prototype.bubbleUp = function (cmp, _arr, val) {
    var idxNr = this.size,
        parentIdxNr = ((idxNr - 1) / 2) | 0;

    while (idxNr > 0 && cmp(_arr[parentIdxNr], val) > 0) {
        fastHeapExchanged.push([_arr[parentIdxNr], val])

        _arr[idxNr] = _arr[parentIdxNr];
        _arr[parentIdxNr] = val;

        idxNr = parentIdxNr;
        parentIdxNr = ((idxNr - 1) / 2) | 0;

        fastHeapOperationCount++
    }
}

SlowHeap.prototype.push = function (val) {
    ++this.size
    this._arr.push(val)
    this.bubbleUp(this.cmp, this._arr, val)
    return this.size
}
FastHeap.prototype.push = function (val) {
    this._arr.push(val);
    this.bubbleUp(this.cmp, this._arr, val);
    return ++this.size;
}

const itemCount = 4000000

const slowHeap = new SlowHeap()
const fastHeap = new FastHeap()

//
// Append the same Number Collection to each Heap:
const numberCollection = []

for (let idxNr = 0; idxNr < itemCount; idxNr++) numberCollection.push(Math.random())

//
// Benchmark for the Slow Heap:
console.time('SlowHeap')

for (let idxNr = 0; idxNr < itemCount; idxNr++) {
    slowHeap.push(numberCollection[idxNr])
}

console.timeEnd('SlowHeap')

//
// Benchmark for the Fast Heap:
console.time('FastHeap')

for (let idxNr = 0; idxNr < itemCount; idxNr++) {
    fastHeap.push(numberCollection[idxNr])
}

console.timeEnd('FastHeap')

//
// Verify the "_arr" from the Slow Heap against the Fast Heap:
for (let idxNr = 0; idxNr < itemCount; idxNr++) {
    if (slowHeap._arr[idxNr + 1] !== fastHeap._arr[idxNr]) console.log('Unequal value found!')
}

if (slowHeapExchanged.length !== fastHeapExchanged.length) console.log('Help! Comp. is not equal.')

for (let idxNr = 0, maxNr = slowHeapExchanged.length; idxNr < maxNr; idxNr++) {
    if (slowHeapExchanged[idxNr][0] !== fastHeapExchanged[idxNr][0] || slowHeapExchanged[idxNr][1] !== fastHeapExchanged[idxNr][1]) {
        console.log('Help!')
    }
}

console.log(slowHeapOperationCount)
console.log(fastHeapOperationCount)