The following implementation in C# using Rx.NET runs in 1min58 in LINQPad on quad core Q6600@2.4ghz:

var listeners =
Enumerable.Range(0, 10000)
.Select(_ => new Subject(Scheduler.TaskPool))
.MemoizeAll();

listeners.Publish(o => o.Zip(o.Skip(1), (l, r) => new { l, r}))
.Run(o => o.l.Subscribe(o.r));

Observable
.Range(0, 10000)
.Delay(TimeSpan.FromMilliseconds(1000))
.Subscribe(listeners.First());

listeners.Last().Last().Dump();

I also have the following F# implementation running in 50s on the same machine (F# interactive):

type Agent = MailboxProcessor

let count = 10000
let now = System.DateTime.Now

Agent.Start (fun inbox ->
async {
while true do
let! msg = inbox.Receive()
if msg = count then
printfn “%A” (System.DateTime.Now – now).TotalMilliseconds })
|> Seq.unfold (fun next ->
let agent = Agent.Start (fun inbox ->
async {
while true do
let! msg = inbox.Receive()
next.Post msg } )
Some (agent, agent))
|> Seq.nth count
|> (fun agent -> for i in 1..count do agent.Post i)

Both code seems to scale pretty well versus the timing I had on my dual core laptop at work (T7400), although I only remember the time for the C#-Rx version at 5min50.

David

I did not spend much time on gathering significant statistics. Getting a readable compact program was far more challenging.

Thanks for this. I’m working my way through the book v-e-r-y slowly as coming from a purely flash development background almost all Erlang concepts are new on me.

But, damn, there’s just something about erlang that makes me want to learn it!