Mirror of forum.nim-lang.org

4157 :: Running multiple sleeps as Async

• Allosteric (orginal) [2018-08-25T17:01:54+02:00] view original

  I'm learning async programming and struggling how to run multiple heavy processes.

  I understand how I can implement it with threadpool,

  import threadpool, times, os, strformat
    proc sleepEcho(time: int) =
      sleep(time)
      echo "slept for ", time, "ms"
    
    let starttime = epochTime()
    
    spawn sleepEcho(2) # I want this,
    spawn sleepEcho(3) # and this to start at once
    
    sync()
    
    echo fmt"Time taken: {(epochTime() - starttime)*1000:.2f}(ms)"
  Run

  which echos

  
    slept for 2ms
    slept for 3ms
    Time taken: 3.00(ms)
  Run

  I've been strugling for a while how to implement this with async.

  The following code is what I've tried,

  import times, asyncdispatch, os, strformat
    proc sleepEcho(time: int) {.async.} =
      sleep(time)
      echo "slept for ", time, "ms"
    
    let starttime = epochTime()
    
    discard sleepEcho(2) # I want this,
    discard sleepEcho(3) # and this to start at once
    
    
    echo fmt"Time taken: {(epochTime() - starttime)*1000:.2f}(ms)"
  Run

  whose result was

  
    slept for 2ms
    slept for 3ms
    Time taken: 5.21(ms)
  Run

  which showed that the second sleepEcho starts AFTER the first sleepEcho terminated.

---

• dom96 (orginal) [2018-08-25T21:41:24+02:00] view original

  Use sleepAsync, not sleep.

---

• Allosteric (orginal) [2018-08-26T05:07:38+02:00] view original

  Thank you for your reply. It went perfectly well.

  import times, asyncdispatch, os, strformat
    
    proc sleepEcho(time: int) {.async.} =
      await sleepAsync(time)
      echo "slept for ", time, "ms"
    
    let a = sleepEcho(2)
    let b = sleepEcho(3)
    
    let starttime = epochTime()
    
    while true:
      poll()
      if a.finished and b.finished:
        break
    
    echo fmt"Time taken: {(epochTime() - starttime)*1000:.2f}(ms)"
  Run

---