Mathf.Approximately(0.0f, float.Epsilon) == true 是正确的行为吗? [英] Is Mathf.Approximately(0.0f, float.Epsilon) == true its correct behavior?

问题描述

我刚刚注意到以下代码返回 true:

I have just noticed that the following code returns true:

Mathf.Approximately(0.0f, float.Epsilon); // true

我已阅读 Mathf.Approximately 文档 并指出:

Approximately() 比较两个浮点数，如果它们在彼此的小值 (Epsilon) 内，则返回 true.

Approximately() compares two floats and returns true if they are within a small value (Epsilon) of each other.

Mathf.Epsilon 文档 指出:

• anyValue + Epsilon = anyValue
• anyValue - Epsilon = anyValue
• 0 + Epsilon = Epsilon
• 0 - Epsilon = -Epsilon

结果，我运行了以下代码，期望它是 false，但它也返回 true.

As a result, I ran the following code, expecting it to be false, but it also returns true.

Mathf.Approximately(0.0f, 2.0f * float.Epsilon); // true

顺便说一句:

Mathf.Approximately(0.0f, 2.0f * float.Epsilon); // true
Mathf.Approximately(0.0f, 3.0f * float.Epsilon); // true
Mathf.Approximately(0.0f, 4.0f * float.Epsilon); // true
Mathf.Approximately(0.0f, 5.0f * float.Epsilon); // true
Mathf.Approximately(0.0f, 6.0f * float.Epsilon); // true
Mathf.Approximately(0.0f, 7.0f * float.Epsilon); // true

Mathf.Approximately(0.0f, 8.0f * float.Epsilon); // false
Mathf.Approximately(0.0f, 9.0f * float.Epsilon); // false

<小时>

问:根据这些证据，我可以肯定地说 Mathf.Approximately 没有根据其文档*正确实现吗?

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Q: Based on that evidence, can I safely say that Mathf.Approximately is not correctly implemented according to its documentation*?

(* 因此，我应该转向不同的解决方案，例如 C# 的浮点比较函数)

(* and as a result, I should move to different solutions, such as the one in Floating point comparison functions for C#)

推荐答案

这里是Unity的public static bool Mathf.Approximately(float a, float b);的反编译代码你可以在末尾看到 * 8.0f ^^，所以确实是一个真正糟糕的记录方法.

Here is the decompiled code of Unity's public static bool Mathf.Approximately(float a, float b); You can see the * 8.0f at the end ^^, so a truely badly documented method indeed.

/// <summary>
/// <para>Compares two floating point values if they are similar.</para>
/// </summary>
/// <param name="a"></param>
/// <param name="b"></param>
public static bool Approximately(float a, float b)
{
   return (double) Mathf.Abs(b - a) < (double) Mathf.Max(1E-06f * Mathf.Max(Mathf.Abs(a),
       Mathf.Abs(b)), Mathf.Epsilon * 8.0f);
}

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