C＃舍入的方式取决于平台？ [英] C# rounding differently depending on platform?

问题描述

我有这小段代码

double s = -2.6114289999999998;
double s7 = Math.Round(s, 7);
double s5 = Math.Round(s, 5);
double s6 = Math.Round(s, 6);

在平台=任何CPU的情况下，我得到

With Platform = Any CPU, I get

s7: -2.611429   
s5: -2.61143    
s6: -2.611429   

使用Platform = x64，我得到

With Platform = x64, I get

s7: -2.6114289999999998 
s5: -2.61143    
s6: -2.6114289999999998

为什么？ （输出从VS的Locals窗口复制）

Why? (Output copied from VS's Locals window)

整段代码为：

    private void btnAlign_Click(object sender, EventArgs e)
    {
        double s = -2.6114289999999998;
        double s7 = Math.Round(s, 7);
        double s5 = Math.Round(s, 5);
        double s6 = Math.Round(s, 6);
    }

推荐答案

值 -2.611429 不能使用64位浮点表示。在32位模式下编译时，该值将改为使用80位（扩展精度）。

The value -2.611429 cannot be represented using 64-bit floating point. When compiling in 32-bit mode the value will instead use 80-bit (extended precision).

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