Java InsertionSort与ShellSort，间隙大小=1？

我有两个用于两种不同排序的实现，InsertionSort和ShellSort

详情如下:

插入排序：

for (int pos = 0; pos < arrayToBeSorted.length; pos++) {
    for (int secondMarker = pos; secondMarker > 0; secondMarker--) {
        int currentValue = arrayToBeSorted[secondMarker];
        int valueBeingCheckedAgainst = arrayToBeSorted[secondMarker - 1];
        if (currentValue > valueBeingCheckedAgainst) {
            break;
        }
        arrayToBeSorted[secondMarker] = arrayToBeSorted[secondMarker - 1];
        arrayToBeSorted[secondMarker - 1] = currentValue;
    }
}

对于ShellSort：

for (int gap = a.length / a.length; gap > 0; gap = (gap / 2)) {
    for (int i = gap; i < a.length; i++) {
        int tmp = a[i];
        int j = i;
        for (; j >= gap && tmp < (a[j - gap]); j -= gap) {
            a[j] = a[j - gap];
        }
        a[j] = tmp;
    }
}

Solving array with: 32000 elements.
Time in milliseconds:357
Time in milliseconds:337
Time in milliseconds:167
Time in milliseconds:168
Time in milliseconds:165
Time in milliseconds:168
Time in milliseconds:167
Time in milliseconds:167
Time in milliseconds:166
Time in milliseconds:167

Solving array with: 128000 elements.
Time in milliseconds:5358
Time in milliseconds:5335
Time in milliseconds:2676
Time in milliseconds:2656
Time in milliseconds:2662
Time in milliseconds:2654
Time in milliseconds:2661
Time in milliseconds:2656
Time in milliseconds:2660
Time in milliseconds:2673

那么，它们之间为什么会有这么大的差异呢？它们基本上是相同的算法

另外，ShellSort的前两次运行耗时更长，而其余运行更快，这怎么可能呢

这是128000个元素的结果，再次插入排序：

Solving array with: 128000 elements.
Time in milliseconds:4292
Time in milliseconds:4267
Time in milliseconds:4241
Time in milliseconds:4252
Time in milliseconds:4253
Time in milliseconds:4248
Time in milliseconds:4261
Time in milliseconds:4260
Time in milliseconds:4333
Time in milliseconds:4261

ShellSort：

for (int gap = a.length / a.length; gap > 0; gap = (gap / 2)) {
    for (int i = gap; i < a.length; i++) {
        int tmp = a[i];
        int j = i;
        for (; j >= gap && tmp < (a[j - gap]); j -= gap) {
            a[j] = a[j - gap];
        }
        a[j] = tmp;
    }
}

Solving array with: 32000 elements.
Time in milliseconds:357
Time in milliseconds:337
Time in milliseconds:167
Time in milliseconds:168
Time in milliseconds:165
Time in milliseconds:168
Time in milliseconds:167
Time in milliseconds:167
Time in milliseconds:166
Time in milliseconds:167

Solving array with: 128000 elements.
Time in milliseconds:5358
Time in milliseconds:5335
Time in milliseconds:2676
Time in milliseconds:2656
Time in milliseconds:2662
Time in milliseconds:2654
Time in milliseconds:2661
Time in milliseconds:2656
Time in milliseconds:2660
Time in milliseconds:2673

---

我确信我传递给方法的数组是完全相同的，它们是随机的。

在插入排序中，您将变得更加复杂

for (int pos = 0; pos < arrayToBeSorted.length; pos++) {
    for (int secondMarker = pos; secondMarker > 0; secondMarker--) {
        int currentValue = arrayToBeSorted[secondMarker];
        int valueBeingCheckedAgainst = arrayToBeSorted[secondMarker - 1];
        if (currentValue > valueBeingCheckedAgainst) {
            break;
        }
        arrayToBeSorted[secondMarker] = arrayToBeSorted[secondMarker - 1];
        arrayToBeSorted[secondMarker - 1] = currentValue;
    }
}

---

在JIT注意到可以用1替换

gap

并消除包装循环之前，它会混淆JIT一段时间。

在插入排序中，您会变得更复杂

for (int pos = 0; pos < arrayToBeSorted.length; pos++) {
    for (int secondMarker = pos; secondMarker > 0; secondMarker--) {
        int currentValue = arrayToBeSorted[secondMarker];
        int valueBeingCheckedAgainst = arrayToBeSorted[secondMarker - 1];
        if (currentValue > valueBeingCheckedAgainst) {
            break;
        }
        arrayToBeSorted[secondMarker] = arrayToBeSorted[secondMarker - 1];
        arrayToBeSorted[secondMarker - 1] = currentValue;
    }
}

---

在JIT注意到

gap

可以替换为1并消除包装环之前，它会混淆JIT一段时间。

感谢您的回答。我取int currentValue=arrayToBeSorted[secondMarker]；搞不清状况（它没有排列成一行[pos]。正如您所说，现在我得到的值大约为3300毫秒，但它仍然没有我的ShellSort实现快。谢谢。复制Shell排序代码，但用1替换

gap

。然后时间应该相等，或者插入排序快一点。谢谢您的回答。我接受了int currentValue=arrayToBeSorted[secondMarker]；超出循环。（它不是arrayToBeSorted[pos]。正如您所说，现在我得到的值大约为3300毫秒，但仍然没有我的ShellSort实现快。谢谢。复制Shell排序代码，但将

gap

替换为1。然后时间应该相等，或者插入排序快一点。