I was looking at the documentation for the Python standard library
yesterday and discovered the 'lru_cache()' function [1]. Python 3.9
defines 'cache()' to be 'lru_cache(maxsize=None)' [2]. This is a
simple cache doesn't require a list and keeping track of size for LRU
replacements [3].
I was curious how this worked since we use a dictionary as a cache in
each GLModule object. The reasoning for this is that the raw data from
the module description needs extra processing before it is used.
Here is a small test program I used:
-----------------------------------------------
#!/usr/bin/env python3
import timeit
function1 = '''\
table = dict()
def fibonacci(value: int) -> int:
if table.get(value) == None:
if value <= 2:
result = 1
else:
result = fibonacci(value - 1) + fibonacci(value - 2)
table[value] = result
return table[value]'''
function2 = '''\
from functools import lru_cache
@lru_cache(maxsize=None)
def fibonacci(value: int) -> int:
if value <= 2:
result = 1
else:
result = fibonacci(value - 1) + fibonacci(value - 2)
return result'''
time1 = timeit.timeit(stmt='fibonacci(300)', setup=function1, number=10000000)
time2 = timeit.timeit(stmt='fibonacci(300)', setup=function2, number=10000000)
print(f'dict: {time1}')
print(f'lru_cache: {time2}')
-----------------------------------------------
Results with Python 3.7:
$ python3.7 example.py
dict: 1.5672868309993646
lru_cache: 0.5880454199996166
Results with Python 3.12:
$ python3.12 example.py
dict: 0.9677453169988439
lru_cache: 0.5958652549998078
Any thoughts on using this feature? The main benefit I see in using
this is that it simplifies code. Right now alot of the functions have
their entire body wrapped in:
if 'makefile-unconditional' not in self.cache:
# do work and then save it
self.cache['makefile-unconditional'] = result
return self.cache['makefile-unconditional']
Using '@lru_cache(maxsize=None)' would let Python deal with all of
this caching for us. It seems that this is pretty standard way to
optimize Python 3 programs [4].
[1] https://docs.python.org/3/library/functools.html#functools.lru_cache
[2] https://docs.python.org/3/library/functools.html#functools.cache
[3]
https://en.wikipedia.org/wiki/Cache_replacement_policies#Least_recently_used_(LRU)
[4]
https://codesearch.debian.net/search?q=%40lru_cache%28maxsize%3DNone%29&literal=1
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