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Aha, but I think the predictions are upper bounds, not upper and lower
bounds. In essence, when they predict that your job will wait for 11.2
hours, with 95% confidence, and your job runs in 15 minutes, then in no
way have they made a prediction in error. Now, if they would have
predicted 1 minute, and it took 15 minutes, then it would have been an
error. It is possible that they do not use knowledge of back-filling,
which would make small jobs run immediately, although they would
predict a long queue wait time, as if no back-filling is enabled. Its
not clear how customized the predictor is, to the scheduler and
features of the LRM, so there is certainly room for being pessimistic
on their predictions.<br>
<br>
Ioan<br>
<br>
Mihael Hategan wrote:
<blockquote cite="mid:1239226320.3974.5.camel@localhost" type="cite">
<pre wrap="">On Wed, 2009-04-08 at 13:58 -0700, Ioan Raicu wrote:
</pre>
<blockquote type="cite">
<pre wrap="">
Mihael Hategan wrote:
</pre>
<blockquote type="cite">
<pre wrap="">You're right. I was trying to say that fundamentally the problem of
uncertainty in queue times will remain by virtue of the fact that the
times when people submit jobs (as well as the amount of jobs) is
unpredictable and it can affect other people's job queue times.
The predictor in the paper answers the question "if you were to submit
your job before the state of the queue changes in any way, what would be
the expected queue time for the job" and not "what will be the queue
time for the job".
</pre>
</blockquote>
<pre wrap="">Yes, its possible that between a query of prediction, and actual
submission, the state of the queues change, and therefore the actual
result change. But, every prediction comes with some error bounds, so
its possible that the change in queue state, might be reflected in the
error bars.
</pre>
</blockquote>
<pre wrap=""><!---->
I don't know... The system predicted that a 2 minute job on Abe would
sit 11.2 hours in the queue and 2.4 hours on QueenBee, but I've ran 20
such jobs on both in the past 15 minutes.
</pre>
</blockquote>
<br>
<pre class="moz-signature" cols="72">--
===================================================
Ioan Raicu, Ph.D.
===================================================
Distributed Systems Laboratory
Computer Science Department
University of Chicago
1100 E. 58th Street, Ryerson Hall
Chicago, IL 60637
===================================================
Email: <a class="moz-txt-link-abbreviated" href="mailto:iraicu@cs.uchicago.edu">iraicu@cs.uchicago.edu</a>
Web: <a class="moz-txt-link-freetext" href="http://www.cs.uchicago.edu/~iraicu">http://www.cs.uchicago.edu/~iraicu</a>
<a class="moz-txt-link-freetext" href="http://dev.globus.org/wiki/Incubator/Falkon">http://dev.globus.org/wiki/Incubator/Falkon</a>
<a class="moz-txt-link-freetext" href="http://dsl-wiki.cs.uchicago.edu/index.php/Main_Page">http://dsl-wiki.cs.uchicago.edu/index.php/Main_Page</a>
===================================================
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