[Python-bugs-list] [ python-Bugs-447945 ] time.time() is not non-decreasing

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Bugs item #447945, was opened at 2001-08-04 08:02
You can respond by visiting: 
http://sourceforge.net/tracker/?func=detail&atid=105470&aid=447945&group_id=5470

Category: Python Library
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Zooko Ozoko (zooko)
Assigned to: Nobody/Anonymous (nobody)
Summary: time.time() is not non-decreasing

Initial Comment:
<p>After spending many hours tracking down weird race
conditions in <a href="http://mojonation.net/">Mojo
Nation</a>, I've finally realized that the problem is
that we assumed that <cite>time.time()</cite> would
return non-decreasing answers.  In fact, successive
calls to <cite>time.time()</cite> can return a
<em>smaller</em> number than previous calls, as
demonstrated by this test (Python 2.0 on debian
woody):</p>
<pre>
import time

x = 0
while 1:
    ox = x
    x = time.time()
    if x < ox:
        print "this is WRONG: ox: %s, x: %s\n" % (ox,
x,)
    else:
        print ".",
</pre>
<p>In order to get the race conditions out of Mojo
Nation, I'm writing a
<cite>non_decreasing_time()</cite>, which does what we
thought <cite>time()</cite> would do.  In fact, I might
just make it <cite>increasing_time()</cite>.  In any
case, the <cite>time.time()</cite> in the standard
library should either be fixed (my preference) to be
non-decreasing, or the documentation should be updated
to warn about the surprise.</p>
<p>Regards,</p>
<p><b><i>Zooko</i></b></p>

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