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gh-106751: Optimize SelectSelector.select() for many iteration case #106879

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merged 2 commits into from
Jul 19, 2023
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gh-106751: Optimize SelectSelector.select() for many iteration case #106879

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gh-106751: Optimize SelectSelector.select() for many iteration case
corona10 Jul 19, 2023
fdab58b
Use frozenset
corona10 Jul 19, 2023
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18 changes: 8 additions & 10 deletions Lib/selectors.py
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Original file line number Diff line number Diff line change
Expand Up @@ -314,17 +314,15 @@ def select(self, timeout=None):
r, w, _ = self._select(self._readers, self._writers, [], timeout)
except InterruptedError:
return ready
r = set(r)
w = set(w)
for fd in r | w:
events = 0
if fd in r:
events |= EVENT_READ
if fd in w:
events |= EVENT_WRITE

key = self._fd_to_key.get(fd)
r = frozenset(r)
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Note: on my system frozenset is slightly slower than set, but the difference is very small

w = frozenset(w)
rw = r | w
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The rw is only used once. You assigned r | w to a variable for readability?

fd_to_key_get = self._fd_to_key.get
for fd in rw:
key = fd_to_key_get(fd)
if key:
events = ((fd in r and EVENT_READ)
| (fd in w and EVENT_WRITE))
ready.append((key, events & key.events))
return ready

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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Library/2023-07-19-10-45-24.gh-issue-106751.3HJ1of.rst
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@@ -0,0 +1,2 @@
Optimize :meth:`SelectSelector.select` for many iteration case. Patch By
Dong-hee Na.