2014-01-25 Guido van Rossum <[email protected]>:
>> It looks like Charles-François doesn't like it:
>> http://bugs.python.org/issue20311#msg209213
>
> Hm.
>
>> My latest patch is more generic because it uses also the resolution of
>> the clock.
>
> That sounds right.
>
> However, now that I see the code, I have a few questions. (Sorry for
> shooting first and asking questions later.)
>
> - Is it intentional that granularity is a public attribute of the event
> loop? (I can see a use case but also abuses and confusion.)
> - Is it intentional that granularity can be *set* by users of the event
> loop?
Ah, it was one point in my TODO list, I forgot to mention it :)
I see two use cases:
- Override the time() method in an event loop: you must be able to
modify the granularity using the new clock resolution. (Same point for
a custom selector.)
- On an embedded device, you may prefer to limit power compution
instead of providing the best reactivity. For an user interface, a
granularity of 10 ms may be enough, no need to react in 1 nanosecond.
I'm not sure that the second use case is related to what I wrote in
_run_once(). Rounding the deadline (away from zero) should maybe be
done in call_later() instead.
I'm fine with a read-only property using a private _granularity attribute.
> - Personally I would write the code differently -- I would not change the
> timeout passed to the selector at all, and when going over the _scheduled
> list I would not use ceil() but write it like this:
>
> now = self.time()
> while self._scheduled:
> handle = self._scheduled[0]
> if handle._when > now + self.granularity:
> break
> handle = heapq.heappop(self._scheduled)
> self._ready.append(handle)
I tested: the unit test pass. I prefer your version because it is
simpler (it doesn't need the math module). See attached patch. Feel
free to commit it, or tell if I can push it.
Victor
diff -r a9270ac18ecc asyncio/base_events.py
--- a/asyncio/base_events.py Sat Jan 25 22:02:14 2014 +0100
+++ b/asyncio/base_events.py Sat Jan 25 23:24:01 2014 +0100
@@ -18,7 +18,6 @@ import collections
import concurrent.futures
import heapq
import logging
-import math
import socket
import subprocess
import time
@@ -605,8 +604,6 @@ class BaseEventLoop(events.AbstractEvent
elif self._scheduled:
# Compute the desired timeout.
when = self._scheduled[0]._when
- # round deadline aways from zero
- when = math.ceil(when / self.granularity) * self.granularity
deadline = max(0, when - self.time())
if timeout is None:
timeout = deadline
@@ -632,9 +629,7 @@ class BaseEventLoop(events.AbstractEvent
self._process_events(event_list)
# Handle 'later' callbacks that are ready.
- now = self.time()
- # round current time aways from zero
- now = math.ceil(now / self.granularity) * self.granularity
+ now = self.time() + self.granularity
while self._scheduled:
handle = self._scheduled[0]
if handle._when > now:
