tets.fs

module Program 

open System.Threading

let delayInMs = 1000
let doAsync nSlow = 
    [ for i = 0 to nSlow - 1 do yield Async.Sleep delayInMs ]
    |> Async.Parallel
    |> Async.RunSynchronously |> ignore<unit array>
    

let runInThreadPool (fn) = 
    let resetEvent = new ManualResetEvent(false);
    let w = System.Threading.WaitCallback(fun _ -> fn (); resetEvent.Set() |> ignore<bool>)
    System.Threading.ThreadPool.QueueUserWorkItem(w) |> ignore<bool>
    resetEvent        

let doSync nSlow = 
    [
        for i = 0 to nSlow - 1 do 
            runInThreadPool (fun () -> System.Threading.Thread.Sleep delayInMs)
    ]
    |> List.iter (fun x -> x.WaitOne() |> ignore<bool>) 


let time str fn = 
    let sw = System.Diagnostics.Stopwatch.StartNew()
    fn () 
    printfn $"'%s{str}' took %i{sw.ElapsedMilliseconds}ms"
    

[<EntryPoint>]
let main args = 
    System.Threading.ThreadPool.SetMaxThreads(System.Environment.ProcessorCount, System.Environment.ProcessorCount) |> printfn "Threads: %b"
    
    let slowToSpin = System.Environment.ProcessorCount + 1

    time "Async" (fun () -> doAsync slowToSpin)
    time "Threads" (fun () -> doSync slowToSpin)

    0

Threads: true
'Async' took 1027ms
'Threads' took 2016ms

C:\Users\se-mikkjel-01\source\repos\ConsoleApp7\ConsoleApp7\bin\Debug\net8.0\ConsoleApp7.exe (process 82760) exited with code 0.
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