Unity/RIDER:乘法运算的顺序效率低下吗? [英] Unity / RIDER: order of multiplication operations is inefficient?

问题描述

骑士IDE通知我以下内容无效

The rider IDE is informing me that the following is inefficient

        transform.Translate(moveDirection * speed * Time.smoothDeltaTime);

，并希望将其重写为

        transform.Translate(Time.smoothDeltaTime * speed * moveDirection);

有人知道为什么吗?

所有乘法，有什么区别?

Its all multiplications, whats the difference ?

对于某些情况，这是speed和moveDirection的值

For some context, here is the value of speed and moveDirection

private Vector3 moveDirection = Vector3.left;

private float speed = 2.5f;

我几乎不理解为什么它更好?

I am little confused in understanding why its better ?

任何人都可以帮忙吗?

谢谢

推荐答案

Vector3具有3个组成部分. X，Y和Z.

Vector3 has 3 components. X, Y and Z.

将Vector3乘以一个值，即可将分量乘以该值.

Multiplying a Vector3 by a value multiplies the components by that value.

由于向量旁边有2个值，因此顺序与结果无关，而与操作数无关.

Since there are 2 values beside the vector, order matters not for the result, but does for the number of operations.

那是因为矢量优先将导致3 + 3 = 6乘法:

That is because vector-first will result in 3+3=6 multiplications:

1. X * =速度
2. Y * =速度
3. Z * =速度
4. X * =时间
5. Y * =时间
6. Z * =时间

vector-last将是1 + 3 = 4乘法:

While vector-last will be 1+3=4 multiplications:

1. scale = speed * time
2. X * =规模
3. Y * =规模
4. Z * =比例

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无论哪种方式，都只是Rider对性能抱有偏执，而优化级别(尽管受到欢迎)绝对不是必需的.

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Either way, it's just Rider being paranoid about performance, and that level of optimization, while welcome, is definitely not required.

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