"Cevahir Demirkiran" <cevo...@gmail.com> wrote in message
news:3f74e020908251648k7b391a09g78b155507b2f2...@mail.gmail.com...
Hi,
I would like to do a floor division by a power of 2 in python to make it
faster than / (modular division in 2.x).
However, it is slower.
What is the reason of that?
I checked them via:
def f2(x,n):
t1 = clock()
r = x/pow(2,n)
t2 = clock()
print (t2-t1)
print r
t2 = clock()
r = x>>n
t3 = clock()
print (t3-t2)
print r
It's not slower on my system, but note the inconsistent results also:
f2(1024,5)
3.47396033483e-06
32
2.19077375482e-06
32
f2(1024,5)
4.84135603429e-06
32
3.08499440393e-06
32
f2(1024,5)
4.6782844052e-06
32
3.77604384028e-06
32
Time it with timeit...
C:\>python -m timeit -n 10000000 -s x=1024 "x>>5"
10000000 loops, best of 3: 0.113 usec per loop
C:\>python -m timeit -n 10000000 -s x=1024 "x/pow(2,5)"
10000000 loops, best of 3: 0.468 usec per loop
Right-shift is over 4x faster.
-Mark
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