On Friday, April 5, 2002, at 01:06 AM, Guido van Rossum wrote:
>> On Thursday, April 4, 2002, at 02:22 PM, Stuart Bishop wrote:
>>
>>> On a side note, writing 'i or False and True' performs much better
I mean (i and True) or (i or False)
>>> than bool(i) in the test implementation, and flow control statements
>>> involving ints are perform much better than flow control using bool.
>>> Will there be a performance degredation in the final version, or
>>> can this be avoided?
>>
>> I fixed my test to not do a global lookup on True and flow control
>> is no longer slower.
>
> Do I take it that you were benchmarking with the Python class shown in
> the PEP?
No - I was benchmarking with the patch posted on Sourceforge (before
PEP285 was checked into CVS), patched into a CVS snapshot taken at
the same time.
Casting to bool using (x and True) or (x or False) : 1.61
Casting to bool using (bool) : 2.68
Flow control on explicit True : 1.42
Flow control on explicit 1 : 0.99
Flow control on variable bound to True : 1.02
Flow control on variable bound to 1 : 0.99
import time
count = 1000000
def test1():
''' Casting to bool using (x and True) or (x or False) '''
nums = xrange(count)
start = time.clock()
for i in nums:
x = (i and True) or (i or False)
end = time.clock()
return end - start
def test2():
''' Casting to bool using (bool) '''
nums = xrange(count)
start = time.clock()
for i in nums:
x = bool(i)
end = time.clock()
return end - start
def test3():
''' Flow control on explicit True '''
nums = xrange(count)
start = time.clock()
for i in nums:
if True:
pass
else:
pass
end = time.clock()
return end - start
def test4():
''' Flow control on explicit 1 '''
nums = xrange(count)
start = time.clock()
for i in nums:
if 1:
pass
else:
pass
end = time.clock()
return end - start
def test5(a = True):
''' Flow control on variable bound to True '''
nums = xrange(count)
start = time.clock()
for i in nums:
if a: pass
else: pass
end = time.clock()
return end - start
def test6(a = 1):
''' Flow control on variable bound to 1 '''
nums = xrange(count)
start = time.clock()
for i in nums:
if a: pass
else: pass
end = time.clock()
return end - start
for f in (test1,test2,test3,test4,test5,test6):
print f.__doc__,': ',f()
--
Stuart Bishop <zen@shangri-la.dropbear.id.au>
http://shangri-la.dropbear.id.au/
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