为什么64位的速度比32位快?

我一直在做一些性能测试,主要是为了了解迭代器和简单for循环之间的区别。作为这项工作的一部分,我创建了一组简单的测试,然后对结果完全感到惊讶。对于某些方法,64位的速度几乎是32位的10倍。

我要找的是为什么会发生这种情况的一些解释。

下面是有问题的3种方法。

private static long ForSumArray(long[] array)
{
    var result = 0L;
    for (var i = 0L; i < array.LongLength; i++)
    {
        result += array[i];
    }
    return result;
}

private static long ForSumArray2(long[] array)
{
    var length = array.LongLength;
    var result = 0L;
    for (var i = 0L; i < length; i++)
    {
        result += array[i];
    }
    return result;
}

private static long IterSumArray(long[] array)
{
    var result = 0L;
    foreach (var entry in array)
    {
        result += entry;
    }
    return result;
}

var repeat = 10000;

var arrayLength = 100000;
var array = new long[arrayLength];
for (var i = 0; i < arrayLength; i++)
{
    array[i] = i;
}

Console.WriteLine("For: {0}", AverageRunTime(repeat, () => ForSumArray(array)));

repeat = 100000;
Console.WriteLine("For2: {0}", AverageRunTime(repeat, () => ForSumArray2(array)));
Console.WriteLine("Iter: {0}", AverageRunTime(repeat, () => IterSumArray(array)));

private static TimeSpan AverageRunTime(int count, Action method)
{
    var stopwatch = new Stopwatch();
    stopwatch.Start();
    for (var i = 0; i < count; i++)
    {
        method();
    }
    stopwatch.Stop();
    var average = stopwatch.Elapsed.Ticks / count;
    return new TimeSpan(average);
}

当我运行这些时,我得到以下结果:

For: 00:00:00.0006080
For2: 00:00:00.0005694
Iter: 00:00:00.0001717

64位

For: 00:00:00.0007421
For2: 00:00:00.0000814
Iter: 00:00:00.0000818

我从中了解到的另一件事是,在数组上进行迭代与for循环一样高效,而且代码更干净、更易于阅读!