[Python-bugs-list] [ python-Bugs-690083 ] test_random fails sometimes

[SourceForge.net]

Bugs item #690083, was opened at 2003-02-20 16:07
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=105470&aid=690083&group_id=5470

Category: Python Library
Group: Python 2.3
Status: Open
Resolution: None
Priority: 5
Submitted By: M.-A. Lemburg (lemburg)
Assigned to: Raymond Hettinger (rhettinger)
Summary: test_random fails sometimes

Initial Comment:
>> test test_random failed -- Traceback (most recent
call last):
>>   File
"/home/lemburg/projects/Python/Dev-Python/Lib/test/test_random.py",
line 25, in test_autoseed
>>     self.assertNotEqual(state1, state2)
>>   File
"/home/lemburg/projects/Python/Dev-Python/Lib/unittest.py",
line 300, in failIfEqual
>>     raise self.failureException, \
>> AssertionError: (2, (1045703145, 318847470,
620640488, 320379787, -1732263717, -1278593374, ...
>
>
>
> This one I don't understand.  Maybe the sleep(1) in
the test isn't
> long enough?


I could not reproduce this, but perhaps using
long(time.time()*256) isn't
safe enough to produce different states in the
WH-generator ?! I'd
add a counter or hash the previous stored state to add some
more noise.


----------------------------------------------------------------------

>Comment By: M.-A. Lemburg (lemburg)
Date: 2003-02-20 18:22

Message:
Logged In: YES 
user_id=38388

Tim, no I'm not sure that it's the WH seed method causing
this. I was basically just guessing here from looking at the
code in random.py.

You could be right in that the time() C function used in _random
is causing the problem.

I'll check with a time.sleep(0.01) call instead of
time.sleep(1).

----------------------------------------------------------------------

Comment By: Tim Peters (tim_one)
Date: 2003-02-20 17:38

Message:
Logged In: YES 
user_id=31435

MAL, do you know that this failed during the WH part of the 
test?  The WH seed() guarantees to produce distinct states 
given distinct inputs, and time.time() all by itself should be 
enough so that it's significantly different between time.sleep
(1) calls.  Multiplying by 256 is just gravy, getting some 
benefit from the fractional seconds too.

The Twister's idea of time-based seeding uses the C time() 
function, though, and that's less robust because it doesn't 
produce "fractional seconds" (as time.time() produces, as 
well as it can).  But it should still be at least a second 
different, unless your system clock got fiddled between calls 
(so, e.g., do you use some web-based time synch service to 
keep your clock up to date?).

----------------------------------------------------------------------

You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=105470&aid=690083&group_id=5470