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<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>(Forgot to do « Reply all »)<o:p></o:p></span></p>
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color:#1F497D'><o:p> </o:p></span></p>
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<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> Nicolas Bertolotti <br>
<b>Sent:</b> Tuesday, July 21, 2009 3:01 PM<br>
<b>To:</b> 'Wesley W. Terpstra'<br>
<b>Subject:</b> RE: [MLton] Problem with recent implementation of
gettimeofday() on MinGW<o:p></o:p></span></p>
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<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>I have observed this in practice.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>I have a binary which ran for 12783 seconds and calls Time.now()
once at the beginning of its execution and once at the end of its execution.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Both calls return the same value which, I guess, is caused by
the face the SML side implementation of Time.now() manages to return the value
from the previous call if the new call returns a smaller value.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>I could not identify the exact location of the overflow by
looking at the code. I suspect the instruction:<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>nowMicroSeconds.QuadPart +=<o:p></o:p></span></p>
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color:#1F497D'>
1000000 * deltaCounter.QuadPart / frequency.QuadPart;<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>But, in my point of view, it could only lead to a failure if the
call occurs after (0xFFFFFFFFFFFFFFFFULL / 10000ULL) / 0xA6E78230ULL = 658767
seconds.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
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<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> Wesley W. Terpstra
[mailto:wesley@terpstra.ca] <br>
<b>Sent:</b> Tuesday, July 21, 2009 2:34 PM<br>
<b>To:</b> Nicolas Bertolotti<br>
<b>Cc:</b> mlton@mlton.org<br>
<b>Subject:</b> Re: [MLton] Problem with recent implementation of gettimeofday()
on MinGW<o:p></o:p></span></p>
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<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>On Tue, Jul 21, 2009 at 10:20 AM, Nicolas Bertolotti <<a
href="mailto:Nicolas.Bertolotti@mathworks.fr">Nicolas.Bertolotti@mathworks.fr</a>>
wrote:<o:p></o:p></p>
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<p class=MsoNormal><span lang=EN-US>It seems to me that the new implementation of
gettimeofday() (the one in the release candidate) is buggy. If a long running
process calls gettimeofday() at the beginning of its execution and then calls
it again after a few hours, it won’t detect the wrap-around in
PerformanceCounter and will not properly rebase the clock.</span><o:p></o:p></p>
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<p class=MsoNormal style='margin-bottom:12.0pt'><br>
Have you observed this in practice? If yes, see if the attached patch helps.
I'm at work, so can't test it beyond seeing if it compiles, but I believe it is
anal enough to catch all possible wrap-arounds.<o:p></o:p></p>
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