[New-bugs-announce] [issue32422] Make OrderedDict can be used for LRU from C
report at bugs.python.org
Sun Dec 24 00:19:02 EST 2017
New submission from INADA Naoki <songofacandy at gmail.com>:
Currently, functools.lru_cache implement own doubly-linked list.
But it is inefficient than OrderedDict because each link node is GC object.
So it may eat more memory and take longer GC time.
I added two private C API for OrderedDict and make lru_cache use it.
* _PyODict_LRUGetItem(): Similar to PyDict_GetItemWithHash() + od.move_to_end(last=True).
* _PyODict_PopItem(): Similar to odict.popitem().
Why I didn't implement C version of move_to_end() is to reduce lookup.
_PyODict_LRUGetItem(key) lookup key once while
od[key]; od.move_to_end(key) lookup key twice.
I'll benchmark it and report result here.
components: Interpreter Core
title: Make OrderedDict can be used for LRU from C
versions: Python 3.7
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