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Brent

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Message 42186 - Posted: 16 Sep 2010, 15:00:27 UTC

I have a task (de_nbody_model1_1_2789_1284175894_3) that is displaying a Computation error after almost 24 hours (23:45:26) of computer time! What might have gone wrong and, more importantly, how can I prevent this from happening in the future? I hate to waste almost a days work for nothing!
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Matt Arsenault
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Message 42188 - Posted: 16 Sep 2010, 15:42:22 UTC - in response to Message 42186.  

It looks like the maximum time exceeded.

We're still working on a way to get a better flops estimate so that BOINC doesn't kill them after some amount of time.

This workunit looks like its radius and mass is pretty close to the worst possible case.
The run times can vary greatly depending on the parameters. Changing multiple parameters at the same time leads to annoying to predict run times. For example, here are some of the graphs I've been making while trying to come up with a prediction using a small number of bodies. Single variable changes lead to large changes like:



Only changing the radii, the run times seem to vary by a factor of 200.




This one's my favorite, although not yet being fit:




[/img]
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Magister

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Message 42328 - Posted: 23 Sep 2010, 18:49:59 UTC - in response to Message 42188.  

Just got one also

http://milkyway.cs.rpi.edu/milkyway/workunit.php?wuid=150393135

and I'm not the only one on this one :-(
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Message 42332 - Posted: 23 Sep 2010, 20:46:55 UTC

This afternoon (12:23 UTC) I finished a workunit after more than 100 hours of run time. This unit named de_nbody_model1_1_35711_1284295325_2 has previously been finished with max. time exceeded error on the wingmen, so I decided to give it a bit more time. I guess it was valid, because it is already purged from the database:
http://milkyway.cs.rpi.edu/milkyway/workunit.php?wuid=150672863

I was not at home this afternoon, so I'm not 100% sure, but if it were invalid, it should still be in the database, right?

Regards
Alex
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Message 42346 - Posted: 24 Sep 2010, 12:55:51 UTC - in response to Message 42328.  

got a second one...

http://milkyway.cs.rpi.edu/milkyway/workunit.php?wuid=150666061

I will stop using Nbody for the moment.
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Message 42352 - Posted: 24 Sep 2010, 19:14:21 UTC

Hi, I got a second one, which received some additional time to be finished. It did today after 185-something hours. Since validation is inconclusive, it is still in the database here, workunit id 150689696, workunit name de_nbody_model1_1_52544_1284309885, task id 196714928. I guess I won't get those 3,956.93 credits claimed? *g*
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Message boards : Number crunching : Computation Error on NBody Model

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