How to achieve Asynchrony instead of Parallelism in F#

Question

(Sticking to a common example with async fetch of many web pages)

How would I spin off multiple (hundreds) of web page requests asynchronously, and then wait for all req

Answer 1

Here's some code that avoids the unknowns, such as web access latency. I am getting under 5% CPU utilization, and about 60-80% efficiency for both sync and async code paths.

open System.Diagnostics

let numWorkers = 200
let asyncDelay = 50

let main =
   let codeBlocks = [for i in 1..numWorkers -> 
                        async { do! Async.Sleep asyncDelay } ]

   while true do
      printfn "Concurrent started..."
      let sw = new Stopwatch()
      sw.Start()
      codeBlocks |> Async.Parallel |> Async.RunSynchronously |> ignore
      sw.Stop()
      printfn "Concurrent in %d millisec" sw.ElapsedMilliseconds
      printfn "efficiency: %d%%" (int64 (asyncDelay * 100) / sw.ElapsedMilliseconds)

      printfn "Synchronous started..."
      let sw = new Stopwatch()
      sw.Start()
      for codeBlock in codeBlocks do codeBlock |> Async.RunSynchronously |> ignore
      sw.Stop()
      printfn "Synchronous in %d millisec" sw.ElapsedMilliseconds
      printfn "efficiency: %d%%" (int64 (asyncDelay * numWorkers * 100) / sw.ElapsedMilliseconds)

main