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Message boards : Number crunching : Climate prediction using twice CPU allocation

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Ed Weber
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Message 43541 - Posted: 10 Dec 2011, 16:08:33 UTC

BOINC setting 50% Climate & 50% SETI
But Climate running High Priority in both 50%s
SETI has been stoped and waiting to run
Problem has been around for over a month and new Climate jobs continue to displace SETI jobs

How do I fix so there is proper sharing?
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Les Bayliss
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Message 43542 - Posted: 10 Dec 2011, 19:16:08 UTC - in response to Message 43541.

Resource share is only an average over a long period of time, say 6 months.

There can be several reasons why the climate models are constantly running in high priority, but the general reason is that BOINC currently considers that it's not going to have enough time to complete the 2 long models that you have before the deadline. (It doesn't know that there's no actual deadline with this project.)

Some things to look at, are the settings that you have for the cache, and the amount of time that you run the computer. The cache settings are Computer is connected to the Internet about every, and Maintain enough work for an additional. These should be kept low for this project so that you don't get too many models downloaded.

One quick fix may be to make sure that you have the project set to No new tasks in the Projects tab, and then to Suspend one of the models, and keep it for later.


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Belfry
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Message 43543 - Posted: 10 Dec 2011, 20:46:59 UTC - in response to Message 43542.
Last modified: 10 Dec 2011, 21:03:23 UTC

Resource share is only an average over a long period of time, say 6 months.

No, it won't take that long for two projects to reach equilibrium. Ed, the main reason you're seeing this behavior is you're running two hadcm3n's (coupled, full resolution ocean's) on a single-core, hyper-threaded Pentium 4. Your seven seconds per timestep is forcing BOINC to run them in high priority, in an effort to finish them before the four-month deadline. You could turn off hyper-threading, which should lower your s/TS by around 40%, but this would limit your processing to one task at a time and somewhat diminish the machine's multi-tasking performance with other applications. Probably the best solution is to avoid hadcm3n's, changing your climateprediction.net preferences to select only the hadam3p models, of which there are plenty right now :)

edit: grammar

Belfry
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Message 43544 - Posted: 10 Dec 2011, 20:57:09 UTC

... with regard to your computation errors, you may want to exclude your anti-virus from scanning the BOINC data directory. This is just my stab in the dark, but it's a fairly common reason for errors mid-task on Windows machines.

Les Bayliss
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Message 43545 - Posted: 10 Dec 2011, 21:22:57 UTC - in response to Message 43543.

6 months isn't about reaching equilibrium, it's about the mental attitude that people need to have when talking about "resource share", when running a mix of WUs, ranging from those project's that have WUs of a few minute/hours, to the very long climate models that take months.


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Belfry
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Message 43546 - Posted: 10 Dec 2011, 22:36:20 UTC
Last modified: 10 Dec 2011, 22:43:38 UTC

I'm running a 1000 hour hadcm3n alongside 8-12 hour WCG tasks on my dual-core laptop right now, and each project gets 50% of CPU time--a core each. There just isn't enough oomph in the OP's machine to crunch one long task requiring 2016 hours (7s/TS) within seventeen weeks of shared time (2856 hours * 50% = 1428 hours). Another solution would be to change the resource allocation to 25% SETI, 75% CPDN, then 2856 * 75% = 2142 would just make the squeeze, but the machine would need to be on 24/7.

Edit: by the way my first solution of turning off hyper-threading will not produce the desired sharing, since that faster s/TS is now only given half the time. I wasn't thinking.

Belfry
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Message 43547 - Posted: 10 Dec 2011, 23:00:41 UTC
Last modified: 10 Dec 2011, 23:10:03 UTC

Hold on, I messed up. The hyper-threading of course allows you to run two tasks at the same time within BOINC so the 7s/TS does fit within the 2856 hours available. But you're downloading two hadcm3n at a time so that is what's cutting your available time in half

Best solution still is to stick to the hadam3p's.

Edited because it's Saturday.

Les Bayliss
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Message 43548 - Posted: 10 Dec 2011, 23:17:44 UTC

And hyperthreading a P4 only gives about 1.25 processors worth of cores. :(


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Ed Weber
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Message 43549 - Posted: 11 Dec 2011, 5:12:26 UTC

Thanks for all your comments.

Unfortunately I don't have enough background to understand many of them.
I shall try the route of "no new jobs" and "suspend" one of the pair till the first is finished. Isn't automatic, but run time is long enough it isn't a burden.
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Ed Weber
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Message 43550 - Posted: 11 Dec 2011, 5:17:44 UTC

Forgot to mention computer is running 24/7
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Belfry
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Message 43551 - Posted: 11 Dec 2011, 17:37:19 UTC

Hi Ed, the crux of the problem is the downloading of two hadcm3n's. It would be great if BOINC would download one task at a time, but this is a shortcoming with BOINC. Even if you set your resource share to 99/1% and your work buffer to 0.1 days, as soon as BOINC requests work for the 1% project it will download the same number of tasks as cores in your machine (real or virtual). BOINC was originally developed at a time when dual-core machines were a dream, and I think the difficulty lies not in rewriting the client, but rather the hundreds of custom server applications and related database interactions.

A workaround is to manually request work: suspend network activity in BOINC, change the number of processors BOINC uses to one (50% for dual-core, 25% for quad-core, etc.), activate the network and update the project for which you need work, then suspend network activity again and set processors back to 100%. Yes, a pain.

Selecting only hadam3p's is the long-term answer (they're about one-fifth as long), but short-term you could suspend SETI and slog through the two hadcm3n's. The aliens can wait ;)

Message boards : Number crunching : Climate prediction using twice CPU allocation


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