循环条件评估 [英] loop condition evaluation

问题描述

只是一个快速问题。

我有一个循环，看起来像这样：

  for（int i = 0; i   

如果是这样，执行这样的操作会更有效率：

  int dimSquare = dim * dim; 
 for（int i = 0; i   

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- 已完成

解决方案

一般来说，值dim在你的循环，它会被重新评估每次。但是，因为在你的例子中不是这样，一个体面的编译器将优化你的代码，你不会看到任何性能的差异。

Just a quick question.

I have a loop that looks like this:

for (int i = 0; i < dim * dim; i++)

Is the condition in a for loop re-evaluated on every loop?

If so, would it be more efficient to do something like this?:

int dimSquare = dim * dim;
for (int i = 0; i < dimSquare; i++)

Thanks

-Faken

解决方案

In general, if you would for example change the value of "dim" inside your loop, it would be re-evaluated every time. But since that is not the case in your example, a decent compiler would optimize your code and you wouldn't see any difference in performance.

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