英文:
Go switch vs if-else efficiency
问题
在Go语言中，switch语句比C语言（和C++）中的switch语句更加灵活，因为它们可以处理布尔表达式的情况，并且可以完全替代大型的else-if梯子，特别是使用默认的switch {...}块。
在Go语言中，使用switch语句是否有任何效率优势？似乎switch语句的灵活性会导致提升的效率丧失。这是否只取决于编译器来判断并查看是否可以生成跳转表？
在使用switch语句与使用if和else语句相比，是否有性能优势？
英文:
In Go, switches are much more flexible than in C (and C++) since they can handle cases of boolean expressions and replace large else-if ladders seemingly entirely, especially with the default switch {...} blocks.
switch {
case x < 5 && y > 2:
//...
case y == 1 || x > 2:
//...
default:
}
Is there any efficiency advantage to using a switch over else-if in Go? It seems that the boosted efficiency would be lost by the switch's flexibility. Is it just up to the compiler to figure it out and see if it can make a jump table?
Is there any performance advantage to using switch over if and else?
答案1
得分: 17
除非你的所有case都是整数常量，否则你就失去了将switch转换为跳转表的可能性。
因此，最好的情况是，如果你只使用整数常量，Go的switch可能与C++的switch等效，但否则它将不比if/else更高效。
英文:
Unless all your case are integral constants then you lose the possibility of transforming the switch to a jump-table.
So, at best, Go's switch might be equivalent to C++'s switch if you only use integral constants, but otherwise it will be no more efficient than if/else.
答案2
得分: 13
完全由编译器来解决并选择一个好的代码实现策略。您可以通过请求编译器输出的汇编清单来了解编译器生成的代码。请参阅Go编译器的-S选项。
英文:
It's completely up to the compiler to figure it out and choose a good implementation strategy for your code. You can always find out what code the compiler is generating by requesting an assembly listing of the compiler output. See the -S option to the Go compiler.
答案3
得分: 3
这对你的应用程序性能来说肯定是无关紧要的。可能还有其他更复杂的情况可以提高性能。像保存一个单独的SQL查询可能相当于100万个if/else/switch语句。
不要过多担心这样的细节，专注于更高层次的事情。
英文:
It's surely irrelevant for your application performance. There is probably other more complex situation where you can improve performance. Like saving a single SQL query is probably like 1 million if/else/switch.
Do not worry much about detail like that and focus on higher level stuff.
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