F#会自动记忆吗?

我有这个密码:

for i in 1 .. 10 do
    let (tree, interval) = time (fun () -> insert [12.; 6. + 1.0] exampletree 128.)
    printfn "insertion time: %A" interval.TotalMilliseconds
    ()

let time f =
    let start = DateTime.Now
    let res = f ()
    let finish = DateTime.Now
    (res, finish - start)

函数insert与此无关,只是它不使用变异,因此每次都返回相同的值。

insertion time: 218.75
insertion time: 0.0
insertion time: 0.0
insertion time: 0.0
insertion time: 0.0
insertion time: 0.0
insertion time: 0.0
insertion time: 0.0
insertion time: 0.0
insertion time: 0.0

问题是为什么代码只计算一次结果(从插入时间开始,结果总是正确和相等的)?另外,如何强制程序多次执行计算(我需要它来进行分析)?

编辑:贾里德提供了正确的答案。现在我知道要找什么了,我可以从 a timeit function for F#

结果如下:

insertion time: 243.4247
insertion time: 0.0768
insertion time: 0.0636
insertion time: 0.0617
insertion time: 0.065
insertion time: 0.0564
insertion time: 0.062
insertion time: 0.069
insertion time: 0.0656
insertion time: 0.0553