为什么 Math.Round(Math.Log(1, 2) + 0.5) 等于零？

Question

我有以下代码：

    public static void Main(string[] args)
    {
        Console.WriteLine($"{Math.Round(0.5)} = round(0.5)");
        Console.WriteLine($"{ToBinaryString(0.5)} = binary 0.5");
        
        Console.WriteLine();
        
        Console.WriteLine($"{Math.Log(1, 2)} = log2(1)");
        Console.WriteLine($"{ToBinaryString(Math.Log(1, 2))} = binary log2(1)");
        
        Console.WriteLine();
        
        Console.WriteLine($"{Math.Round(Math.Log(1, 2) + 0.5)} = round(log2(1) + 0.5)");
        Console.WriteLine($"{ToBinaryString(Math.Log(1, 2) + 0.5)} = binary log2(1) + 0.5");
        
        Console.WriteLine();
        
        Console.WriteLine($"{Math.Round(0.0 + 0.5)} = round(0.0 + 0.5");
        Console.WriteLine($"{ToBinaryString(0.0 + 0.5)} = binary 0.0 + 0.5");
        
        Console.WriteLine();
        
        Console.WriteLine($"{Math.Log(1, 2) + 0.5 == 0.5} = Math.Log(1, 2) + 0.5 == 0.5");
        Console.WriteLine($"{Math.Log(1, 2) == 0.0} = Math.Log(1, 2) == 0.0");
    }
    
    static string ToBinaryString(double value)
    {
        const int bitCount = sizeof(double) * 8;
        long intValue = System.BitConverter.ToInt64(BitConverter.GetBytes(value), 0);
        return Convert.ToString(intValue, 2).PadLeft(bitCount, '0');
    }

输出为：

1 = round(0.5)
0011111111100000000000000000000000000000000000000000000000000000 = binary 0.5

0 = log2(1)
0000000000000000000000000000000000000000000000000000000000000000 = binary log2(1)

0 = round(log2(1) + 0.5) // ???? Why ????
0011111111100000000000000000000000000000000000000000000000000000 = binary log2(1) + 0.5

1 = round(0.0 + 0.5
0011111111100000000000000000000000000000000000000000000000000000 = binary 0.0 + 0.5

True = Math.Log(1, 2) + 0.5 == 0.5
True = Math.Log(1, 2) == 0.0

根据输出，我可以说，

Math.Log(1, 2)

恰好是

0

，而

Math.Log(1, 2) + 0.5

恰好是

0.5

。我认为是的，因为它们在内存中的表示是相等的。所以

double

类型的精度在这种情况下没有任何影响。如果我错了，请修复我。

但是

Math.Round(Math.Log(1, 2) + 0.5)

不等于

Math.Round(0.5)

或

Math.Round(0.0 + 0.5)

。怎么解释呢？