我有一些code，做了很多的64位整数比较，但它必须考虑到数字的长度，因为如果它被格式化为一个字符串。我不能改变调用code，只有功能。

I have some code that does a lot of comparisons of 64-bit integers, however it must take into account the length of the number, as if it was formatted as a string. I can't change the calling code, only the function.

最简单的方法（除了的ToString（）的长度。）是：

The easiest way (besides .ToString().Length) is:

(int)Math.Truncate(Math.Log10(x)) + 1;

不过，执行相当差。由于我的应用程序只发送正值，且长度相当均匀2和9之间的分布（与朝9一些偏见），我precomputed的值，并有if语句：

However that performs rather poorly. Since my application only sends positive values, and the lengths are rather evenly distributed between 2 and 9 (with some bias towards 9), I precomputed the values and have if statements:

static int getLen(long x) {
    if (x < 1000000) {
        if (x < 100) return 2;
        if (x < 1000) return 3;
        if (x < 10000) return 4;
        if (x < 100000) return 5;
        return 6;
    } else {
        if (x < 10000000) return 7;
        if (x < 100000000) return 8;
        if (x < 1000000000) return 9; 
        return (int)Math.Truncate(Math.Log10(x)) + 1; // Very uncommon
    }
}

此允许长度平均为4比较来计算。

This lets the length be computed with an average of 4 compares.

那么，还有没有其他的技巧，我可以使用，使这个功能更快？

So, are there any other tricks I can use to make this function faster?

编辑：这将运行32位code（Silverlight的）

This will be running as 32-bit code (Silverlight).

更新：

我把诺曼的建议，改变了IFS张望了一下导致平均只有3比较。按照肖恩的评论，我删除了Math.Truncate。一起，这促进了约10％的事情。谢谢！

I took Norman's suggestion and changed the ifs around a bit to result in an average of only 3 compares. As per Sean's comment, I removed the Math.Truncate. Together, this boosted things about 10%. Thanks!

推荐答案

两点建议：

该组合可能不会买你多少，除非分布是非常偏斜。

This combination probably doesn't buy you much unless the distribution is very skew.