performance - 调用库和直接操作效率有区别吗？

Question

不确定我的措辞是否正确，但要点是:

调用 math.Pow(x, 2) 是否更有效，还是应该使用 x*x？

我已经尝试过它们，但不幸的是，我无法检测到我的测试文件中可能存在的微秒差异。

Answer 1

通常函数调用需要一些额外的时间(例如，传递参数并将其返回到函数或从函数返回)。但对于简单的情况，Go 可以进行一些优化，例如内联。 如文档CompilerOptimizations中所述有几个条件:

Only short and simple functions are inlined. To be inlined a function must conform to the rules:

• function should be simple enough, the number of AST nodes must less than the budget (80);
• function doesn't contain complex things like closures, defer, recover, select, etc;
• function isn't prefixed by go:noinline; function isn't prefixed by go:uintptrescapes,
• since the escape information will be lost during inlining;
• function has body; etc.
• gc: 1.0+
• gccgo: -O1 and above.