Add async solution to Nim (#482)

Author: Clemente90

bench/algorithm/coro-prime-sieve/3.nim

@@ -0,0 +1,93 @@
+import std/asyncdispatch
+import std/os
+import std/strutils
+
+
+
+##
+## # Channel[T]
+##
+## As far as I know Nim's asyncdispatch has many features but lacks an awaitable
+## channel type. It uses Futures as the work horse of async communication instead.
+##
+## I craeted a very simple async-awaitable channel type so I can match the
+## reference Go implementation this benchmark originated from.
+##
+
+type Channel[T] = object
+  ## An simple one-item, async-awaitable Channel.
+  untilIsEmpty: Future[void]
+  untilIsFull: Future[void]
+  val: T
+
+
+proc newChannel[T](): ref Channel[T] =
+  ## Initializer. Allocate a new ref Channel object on the heap.
+  result = new Channel[T]
+  result[].untilIsEmpty = newFuture[void]()
+  result[].untilIsFull = newFuture[void]()
+  result[].untilIsEmpty.complete()
+
+
+proc send[T](chan: ref Channel[T], val: T) {.async.} =
+  # Accept val if empty, otherwise, suspend until empty.
+  await chan[].untilIsEmpty
+  chan[].untilIsEmpty = newFuture[void]()
+  chan[].val = val
+  chan[].untilIsFull.complete()
+
+
+proc recv[T](chan: ref Channel[T]): Future[T] {.async.} =
+  # Return held val if full, otherwise, suspend until full.
+  await chan[].untilIsFull
+  chan[].untilIsFull = newFuture[void]()
+  result = chan[].val
+  chan[].untilIsEmpty.complete()
+
+
+
+##
+## # Benchmark
+##
+## Below, "Concurrent Prime Sieve" that matches Go reference implementation.
+##
+##   [X] Uses coroutines.
+##   [X] Uses a coroutine scheduler.
+##   [X] Uses an async channel for communitating between coroutines.
+##   [X] Same 3 functions, structured like the reference.
+##
+
+
+proc generate(chan: ref Channel[int]) {.async.} =
+  ## Send the sequence 2, 3, 4, ... to cannel `chan`.
+  for i in 2 .. int.high:
+    await chan.send(i)
+
+
+proc filter(inChan, outChan: ref Channel[int], prime: int) {.async.} =
+  ## Copy the values from channel `inChan` to channel `outChan`, removing those
+  ## divisible by `prime`.
+  while true:
+    let i = await inChan.recv() # revieve value from `inChan`
+    if i mod prime != 0:
+      await outChan.send(i) # send `i` to `outChan`
+
+
+proc main(n: int) {.async.} =
+  ## The prime sieve: Daisy-chain filter processes.
+  var firstChan = newChannel[int]() # craete a new channel
+  asyncCheck generate(firstChan) # launch generate coroutine
+  for i in 0 ..< n:
+    let prime = await firstChan.recv()
+    echo prime
+    var secondChan = newChannel[int]()
+    asyncCheck filter(firstChan, secondChan, prime)
+    firstChan = secondChan
+
+
+when isMainModule:
+
+  let n = if paramCount() > 0: parseInt(paramStr(1)) else: 100
+  waitFor main(n)
+
+

bench/bench_nim.yaml

@@ -32,6 +32,7 @@ problems:
   - name: coro-prime-sieve
     source:
       - 1.nim
+      - 3.nim
   - name: lru
     source:
       - 1.nim