concurrency/parallelism using Asyncs

c-vs-p.fsx

#r "nuget: Nito.AsyncEx, 5.1.2"
open System.Threading
open System.Threading.Tasks
open Nito.AsyncEx

let work x y =
    async {
        do! Async.Sleep 1
        return 1 + 2
    }


let printlock = obj()
let inline log tag msg =
   lock printlock (fun _ ->
      printfn $"[%s{tag}]\t%s{msg}"
   )

let sendWorkers ctx x y =
    async {
        let workId = string (x,y)
        do! Async.SwitchToContext ctx
        log workId $"Starting work on thread {Thread.CurrentThread.ManagedThreadId}"
        let! workerBee1 = work (x) (y) |> Async.StartChild
        log workId $"Starting subitem 2 on {Thread.CurrentThread.ManagedThreadId}"
        let! workerBee2 = work (x) (y + 1) |> Async.StartChild
        log workId $"Starting subitem 3 on {Thread.CurrentThread.ManagedThreadId}"
        let! workerBee3 = work (x) (y + 2) |> Async.StartChild

        // collect results
        log workId $"waiting for results on {Thread.CurrentThread.ManagedThreadId}"
        let! result1 = workerBee1
        let! result2 = workerBee2
        let! result3 = workerBee3

        //print results
        log workId $"done on {Thread.CurrentThread.ManagedThreadId}"
    }

let ROWS = 10

// use this block to show off concurrency
let asyncCtx = new AsyncContext()
AsyncContext.Run<unit[]>(System.Func<Task<unit[]>>(fun () ->
    let ctx = SynchronizationContext.Current
    Seq.init ROWS (fun i -> sendWorkers ctx i 0)
    |> Async.Parallel
    |> Async.StartAsTask
))
asyncCtx.Execute()

// use this block to show off parallelism
// Seq.init ROWS (fun i -> sendWorkers null i 0)
// |> Async.Parallel
// |> Async.RunSynchronously

// System.Console.ReadLine() |> ignore