写了个函数作为装饰器为Fibonacci数列做缓存,做了一下性能比较。
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
| #!/usr/bin/python
# coding: UTF-8
import datetime
now = datetime.datetime.now
from functools import wraps
def cache(func):
caches = {}
@wraps(func)
def wrap(*args):
if args not in caches:
caches[args] = func(*args)
return caches[args]
return wrap
def fib(num):
if num < 2:
return 1
return fib(num-1) + fib(num-2)
fib_with_cache = cache(fib)
start = now()
for i in range(10):
fib(30)
end = now()
print "Fib without cache costs: %r" % (end - start)
start = now()
for i in range(10):
fib_with_cache(30)
end = now()
print "Fib with cache costs: %r" % (end - start)
|
输出结果:
Fib without cache costs: datetime.timedelta(0, 6, 219000)
Fib with cache costs: datetime.timedelta(0, 0, 672000)
当然,正确的使用Fibonacci数列的方法应该是在函数体内使用循环,而不是使用递归。多层递归很容易对性能造成非常严重的影响。
Have a nice day!