performance - 列表理解与 List.concat

Question

我的(回合制)游戏代码中有以下函数，其中列出了游戏中玩家的所有合法 Action :

let moves game = 
    let movesType1 game = ... //returns Move list
    let movesType2 game = ... //returns Move list
    let movesType3 game = ... //returns Move list

    List.concat [ (movesType1 game); (movesType2 game); (movesType3 game) ]

现在我想知道如果我使用列表理解和 yield! 执行以下操作会有什么区别:

let moves game = 
    let movesType1 game = ... //returns Move list
    let movesType2 game = ... //returns Move list
    let movesType3 game = ... //returns Move list

    [ yield! movesType1 game
      yield! movesType2 game
      yield! movesType3 game ]

在某些情况下我可能会多次使用这个函数，所以我有点担心性能。

Answer 1

这是一个简单的测试脚本，测量两个实现之间的时间差异:

let test1 () = List.concat [ [1..10000]; [1..10000]; [1..10000] ]

let test2 () = [ yield! [1..10000]
                 yield! [1..10000]
                 yield! [1..10000] ]

let runTest testImplementation = 
    for i in 1..1000 do
        testImplementation () |> ignore
#time
runTest test1 //Real: 00:00:02.353, CPU: 00:00:02.371, GC gen0: 143, gen1: 96, gen2: 1
#time
System.GC.WaitForFullGCComplete() |> ignore
#time
runTest test2 //Real: 00:00:03.739, CPU: 00:00:03.712, GC gen0: 185, gen1: 185, gen2: 0
#time

看起来 List.concat 更好一点，但是像所有性能方面的事情一样，您应该衡量性能优势是否真的对您的用例很重要。