Yield results on demand using a mem chan

examples/parallelism/concurrent_actors_primes.py

@@ -24,7 +24,8 @@ PRIMES = [
     112272535095293,
     115280095190773,
     115797848077099,
-    1099726899285419]
+    1099726899285419,
+]
 
 
 def is_prime(n):
@@ -50,17 +51,10 @@ async def worker_pool(workers=4):
 
     """
 
-    async with tractor.open_nursery(
-        loglevel='ERROR',
-
-        # uncomment to use ``multiprocessing`` fork server backend
-        # which gives a startup time boost at the expense of nested
-        # processs scalability
-        # start_method='forkserver')
-    ) as tn:
+    async with tractor.open_nursery() as tn:
 
         portals = []
-        results = []
+        snd_chan, recv_chan = trio.open_memory_channel(len(PRIMES))
 
         for i in range(workers):
 
@@ -79,35 +73,37 @@ async def worker_pool(workers=4):
         ) -> List[bool]:
 
             # define an async (local) task to collect results from workers
-            async def collect_portal_result(func, value, portal):
-
-                results.append((value, await portal.run(func, n=value)))
+            async def send_result(func, value, portal):
+                await snd_chan.send((value, await portal.run(func, n=value)))
 
             async with trio.open_nursery() as n:
 
                 for value, portal in zip(sequence, itertools.cycle(portals)):
-
                     n.start_soon(
-                        collect_portal_result,
+                        send_result,
                         worker_func,
                         value,
                         portal
                     )
 
-            return results
+                # deliver results as they arrive
+                for _ in range(len(sequence)):
+                    yield await recv_chan.receive()
 
         yield map
 
-        # tear down all "workers"
+        # tear down all "workers" on pool close
         await tn.cancel()
 
 
 async def main():
+
     async with worker_pool() as actor_map:
 
         start = time.time()
         # for number, prime in zip(PRIMES, executor.map(is_prime, PRIMES)):
-        for number, prime in await actor_map(is_prime, PRIMES):
+        async for number, prime in actor_map(is_prime, PRIMES):
+
             print(f'{number} is prime: {prime}')
 
         print(f'processing took {time.time() - start} seconds')