The test below is done with Python 2.4a1 compiled from source, but
the same thing happens with Debian's python2.3_2.3.4-2.
Python 2.4a1 (#1, Jul 11 2004, 12:20:32)
[GCC 3.3.4 (Debian)] on linux2
Type "help", "copyright" , "credits" or "license" for more information. import timeit
import time
t=timeit.Timer( "pass","pass",t ime.time)
print t.timeit()
0.0560228824615 print t.repeat(1)
[0.0427510738372 80273]
The results are consistent if repeated, i.e. timeit always produces
about 0.056 and repeat always produces about 0.043.
It doesn't help to do:
for i in range(10):
print t.timeit()
vs.
print t.repeat(10)
The problem happens on both machines I've tested it on. One is a
desktop. No other jobs running.
With Python 2.3, the results are affected by the setting of the
PYTHONPATH environment variable. With it unset or set to an empty
directory /tmp/foo I get results like above. With it set to an empty
directory /tmp/python, I get results that agree with each other.
But with Python 2.4, all three settings give results that disagree.
If I use the ipython shell, things are even worse: the results
disagree by a factor of almost 2!
I've read timeit.py and can't see how this might happen.
Any thoughts?
Dan 3  2084 
Can anyone confirm whether this discrepancy happens with other
installations of python on other hardware/OS's? It's a bit
disconcerting.
Thanks,
Dan
Dan Christensen <jd*@uwo.ca> writes: The test below is done with Python 2.4a1 compiled from source, but
the same thing happens with Debian's python2.3_2.3.4-2.
Python 2.4a1 (#1, Jul 11 2004, 12:20:32)
[GCC 3.3.4 (Debian)] on linux2
Type "help", "copyright" , "credits" or "license" for more information. import timeit
import time
t=timeit.Timer( "pass","pass",t ime.time)
print t.timeit() 0.0560228824615 print t.repeat(1)
[0.0427510738372 80273]
The results are consistent if repeated, i.e. timeit always produces
about 0.056 and repeat always produces about 0.043.
It doesn't help to do:
for i in range(10):
print t.timeit()
vs.
print t.repeat(10)
The problem happens on both machines I've tested it on. One is a
desktop. No other jobs running.
With Python 2.3, the results are affected by the setting of the
PYTHONPATH environment variable. With it unset or set to an empty
directory /tmp/foo I get results like above. With it set to an empty
directory /tmp/python, I get results that agree with each other.
But with Python 2.4, all three settings give results that disagree.
If I use the ipython shell, things are even worse: the results
disagree by a factor of almost 2!
I've read timeit.py and can't see how this might happen.
Any thoughts?
Dan
Dan Christensen wrote: Can anyone confirm whether this discrepancy happens with other
installations of python on other hardware/OS's? It's a bit
disconcerting.
Measured on an aging Suse 8.1:
Python 2.3.3 (#1, Jan 3 2004, 13:57:08)
[GCC 3.2] on linux2
Type "help", "copyright" , "credits" or "license" for more informa
tion. import timeit, time
t = timeit.Timer()
t.timeit()
0.0541989803314 20898 t.repeat(1)
[0.0538489818572 99805] t.timeit()
0.0617580413818 35938 t.repeat(1)
[0.0531320571899 41406] t.timeit()
0.0553798675537 10938 t.repeat(1)
[0.0747120380401 61133] tt = t.repeat(1000)
tt.sort()
tt[0]
0.0530700683593 75 tt[-1]
0.0565237998962 40234
And now what?
I'd just stick with the commandline's "best of N" strategy. Also, I would
expect the "pass" statement to be the fastest to execute and therefore the
least accurate to measure.
Peter
Dan Christensen wrote: Hmm, if I type this at the python prompt:
r = []
for i in range(1): # Note: only one loop!
ti = t.timeit()
r.append(ti)
print r
I get data that agrees with t.repeat but disagrees with:
....
t.timeit()
You could try "intermedia te simplifications " to spot the culprit:
r = [None]
for i in range(1):
r[i] = t.timeit()
and
for i in range(1):
ti = t.timeit()
I've no idea what's happening.
Peter This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
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