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Track the cache size directly.

This commit is contained in:
Raymond Hettinger 2012-04-29 18:09:02 -07:00
parent c204348906
commit b6b98c093e
1 changed files with 11 additions and 10 deletions
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21
Lib/functools.py
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@ -168,15 +168,14 @@ def lru_cache(maxsize=100, typed=False):
# to allow the implementation to change (including a possible C version).
# Constants shared by all lru cache instances:
kwd_mark = (object(),) # separate positional and keyword args
sentinel = object() # unique object used to signal cache misses
_len = len # localize the global len() function
kwd_mark = (object(),) # separate positional and keyword args
sentinel = object() # unique object used to signal cache misses
PREV, NEXT, KEY, RESULT = 0, 1, 2, 3 # names for the link fields
def decorating_function(user_function):
cache = {}
hits = misses = 0
hits = misses = currsize = 0
cache_get = cache.get # bound method to lookup a key or return None
lock = Lock() # because linkedlist updates aren't threadsafe
root = [] # root of the circular doubly linked list
@ -209,7 +208,7 @@ def lru_cache(maxsize=100, typed=False):
def wrapper(*args, **kwds):
# simple caching without ordering or size limit
nonlocal hits, misses
nonlocal hits, misses, currsize
key = make_key(args, kwds, typed) if kwds or typed else args
result = cache_get(key, sentinel)
if result is not sentinel:
@ -218,13 +217,14 @@ def lru_cache(maxsize=100, typed=False):
result = user_function(*args, **kwds)
cache[key] = result
misses += 1
currsize += 1
return result
else:
def wrapper(*args, **kwds):
# size limited caching that tracks accesses by recency
nonlocal root, hits, misses
nonlocal root, hits, misses, currsize
key = make_key(args, kwds, typed) if kwds or typed else args
with lock:
link = cache_get(key)
@ -241,11 +241,12 @@ def lru_cache(maxsize=100, typed=False):
return result
result = user_function(*args, **kwds)
with lock:
if _len(cache) < maxsize:
if currsize < maxsize:
# put result in a new link at the front of the queue
last = root[PREV]
link = [last, root, key, result]
cache[key] = last[NEXT] = root[PREV] = link
currsize += 1
else:
# use root to store the new key and result
root[KEY] = key
@ -261,15 +262,15 @@ def lru_cache(maxsize=100, typed=False):
def cache_info():
"""Report cache statistics"""
with lock:
return _CacheInfo(hits, misses, maxsize, len(cache))
return _CacheInfo(hits, misses, maxsize, currsize)
def cache_clear():
"""Clear the cache and cache statistics"""
nonlocal hits, misses
nonlocal hits, misses, currsize
with lock:
cache.clear()
root[:] = [root, root, None, None]
hits = misses = 0
hits = misses = currsize = 0
wrapper.cache_info = cache_info
wrapper.cache_clear = cache_clear