a timeit function for F#

Question

I am trying to write something like

let timeit (x:'a->'b) =
    let start = System.DateTime.Now
    x
    let duration = System.DateTime.Now - start
    printfn "time usage = %A" duration.Milliseconds 
    ()

it works for

let matrixtest() =
    let x = vector[1.;2.;4.]
    let y = matrix[[1.;2.;4.;];[3.;4.;9.;]]
    printfn "%A" (y * x)
    ()

but not for

let rec fib x = 
        match x with
        | 0 | 1 -> 1
        | n -> fib (n-1) + fib (n-2)

sa F# is static typed.

Any idea? Thanks.

Answer 1

Putting it together

let timeit f v = 
    let watch = new System.Diagnostics.Stopwatch()
    watch.Start()
    let res = f v 
    watch.Stop()
    printfn "Needed %f ms" (watch.Elapsed.TotalMilliseconds)
    res