Gjallarhorn

Output.txt

Creating signal...
A dependency has changed. Called from thread ID 1
Setting m1...
Sleeping 200 ms
A dependency has changed. Called from thread ID 3
Signal value is now 4. thread ID: 3
Signal value is now 4. thread ID: 4
Thread awake again
Setting m2...
Finished
A dependency has changed. Called from thread ID 5
Signal value is now 5. thread ID: 5
Signal value is now 5. thread ID: 3

Program.fs

open Gjallarhorn
open System.Threading

[<EntryPoint>]
let main argv =
  let m1 = Mutable.create 1L
  let m2 = Mutable.create 2L

  let sync_ctx = System.Threading.SynchronizationContext()

  printfn "Creating signal..."
  let signal =
    (m1, m2)
    ||> Signal.map2
      (fun a b ->
        printfn "A dependency has changed. Called from thread ID %d" (Thread.CurrentThread.ManagedThreadId)
        a + b)
    |> Signal.observeOn sync_ctx

  use _sub = signal.Subscribe (fun res -> printfn "Signal value is now %d. thread ID: %d" res (Thread.CurrentThread.ManagedThreadId))
  
  printfn "Setting m1..."
  m1.Value <- 2L

  printfn "Sleeping 200 ms"
  System.Threading.Thread.Sleep(200)
  printfn "Thread awake again"

  printfn "Setting m2..."
  m2.Value <- 3L

  printfn "Finished"
  System.Console.ReadLine() |> ignore
  0

Question.txt

Seems like there are 2 more subscription messages than expected (line 7 and line 13 of the output). 

They go away if line 18 of the code is removed. 

Is this expected?