from https://github.com/Microsoft/visualfsharp/pull/513#issuecomment-115627731

513b.fs

module Program

open Perf
open System
open System.Diagnostics

[<EntryPoint>]
let main argv =
    printfn "%s" Id.Name

    // create lots of lists to try not to get cache benefits
    let lists = 
        Array.init 1000000 (fun i ->
            List.init 10 (fun j ->
                if i % 2 = 0 then -j else j))

    let sw = Stopwatch.StartNew ()
    let r = Random 42
    let mutable count = 0
    for i=0 to 1000000 do
        let a = lists.[r.Next lists.Length]
        let b = lists.[r.Next lists.Length]
        count <- count + if a = b then 1 else 0

    printfn "%A (%A)" sw.ElapsedMilliseconds count

    0