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Eric Mendelsohn
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Message 70006 - Posted: 30 Jul 2020, 0:06:07 UTC

Hey everyone,

I just wanted to let everyone know that new Nbody runs have been put up on MW@home. The last set of runs started converging nicely, so we are confident this next set of runs will converge as well. The names of these runs are:
-de_nbody_07_29_2020_v176_40k__data__1
-de_nbody_07_29_2020_v176_40k__data__2
-de_nbody_07_29_2020_v176_40k__data__3

Please let us know if you have any trouble with these runs. Thank you all for your continued support.

-Eric
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Awadh Bihari Pandey
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Message 70007 - Posted: 31 Jul 2020, 15:54:29 UTC - in response to Message 70006.  

Yes
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mippi

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Message 70008 - Posted: 1 Aug 2020, 1:27:45 UTC - in response to Message 70006.  

What can I do to get the NBody tasks? I only receive Separation tasks. I have been with Milkyway@home for a while I have never received NBody jobs.
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ProfileKeith Myers
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Message 70009 - Posted: 1 Aug 2020, 8:27:54 UTC - in response to Message 70008.  

Have you configured your account to accept cpu and N-body work?
https://milkyway.cs.rpi.edu/milkyway/prefs.php?subset=project
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Michael McMullen

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Message 70010 - Posted: 3 Aug 2020, 18:02:00 UTC

Got a hang on de_nbody_07_29_2020_v176_40k_data_3_1596028202__76964_1
stops making progress for hours (task should be 5 to 10 minutes). Was not problem on previous groups of Nbody. After short suspend runs to completion in reasonable time. Best if these sorts of things errored out rather than tie up all Nbodys until human intervention.
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Michael McMullen

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Message 70011 - Posted: 3 Aug 2020, 18:15:15 UTC - in response to Message 70010.  

Also when Nbody gets buffed up, ability to run it on the gpu would be good, as a lot of machines these days have Radeon VII, Titan V, etc. that can really chew through double precision tasks and have a lot of memory, not being partly crippled for compute tasks like purely gameing cards. They don't do so well on the separations as they might as each only takes 12 to 20 sec and a fair amount of time is spent on loading and unloading them in the gpu, and the number sent gets used up fast and there is no work available for a while. Probably would not work well for Nbody if quad or greater precision is needed.
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mippi

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Message 70015 - Posted: 5 Aug 2020, 1:27:11 UTC - in response to Message 70009.  

Does it mean that the NBody application works on CPU only? If not, how can I enable the app on my account? I cannot see any option to do that.
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Falconet

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Message 70017 - Posted: 5 Aug 2020, 19:01:56 UTC - in response to Message 70015.  

Does it mean that the NBody application works on CPU only? If not, how can I enable the app on my account? I cannot see any option to do that.



CPU only.
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bfromcolo

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Message 70018 - Posted: 6 Aug 2020, 13:18:46 UTC
Last modified: 6 Aug 2020, 13:28:50 UTC

I have a 12 core (24 thread) CPU and am getting 16 thread tasks, so its only running one at a time. CPU utilization is very low for a couple minutes, and then peaks around 50% for the rest of the task. Is there an app_config that would allow specifying running 2 x 12 or 3 x 8 thread tasks? It would improve efficiency greatly.

Edit I think I figured it out.

<app_config>
<app>
<name>milkyway_nbody</name>
<max_concurrent>3</max_concurrent>
</app>
<app_version>
<app_name>milkyway_nbody</app_name>
<plan_class>mt</plan_class>
<avg_ncpus>8</avg_ncpus>
</app_version>
</app_config>
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Jim1348

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Message 70019 - Posted: 6 Aug 2020, 14:18:31 UTC - in response to Message 70018.  
Last modified: 6 Aug 2020, 14:19:10 UTC

Yes. I run only one core per work unit. They don't take much memory anyway (only 16 MB).
I don't see the point of running more cores. They just disrupt the other projects.

But I run mine 24/7, and they sometimes run for over a day. If you need to complete them faster, then of course more cores would help.
But I think you lose a little efficiency with more cores.

<app_config>
  <project_max_concurrent>16</project_max_concurrent>
  <app>
    <name>milkyway_nbody</name>
    <fraction_done_exact/>
    </app>
  <app_version>
    <app_name>milkyway_nbody</app_name>
    <plan_class>mt</plan_class>
    <avg_ncpus>1</avg_ncpus>
  </app_version>
</app_config>
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ProfileKeith Myers
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Message 70020 - Posted: 6 Aug 2020, 15:55:21 UTC - in response to Message 70018.  
Last modified: 6 Aug 2020, 15:56:35 UTC

I have a 12 core (24 thread) CPU and am getting 16 thread tasks, so its only running one at a time. CPU utilization is very low for a couple minutes, and then peaks around 50% for the rest of the task. Is there an app_config that would allow specifying running 2 x 12 or 3 x 8 thread tasks? It would improve efficiency greatly.

Edit I think I figured it out.

<app_config>
<app>
<name>milkyway_nbody</name>
<max_concurrent>3</max_concurrent>
</app>
<app_version>
<app_name>milkyway_nbody</app_name>
<plan_class>mt</plan_class>
<avg_ncpus>8</avg_ncpus>
</app_version>
</app_config>

Actually the correct method of defining mt app is provided in the BOINC configuration document.
https://boinc.berkeley.edu/wiki/Client_configuration#Application_configuration

They provide an example.

[<app_version>
<app_name>Application_Name</app_name>
[<plan_class>mt</plan_class>]
[<avg_ncpus>x</avg_ncpus>]
[<ngpus>x</ngpus>]
[<cmdline>--nthreads 7</cmdline>]
</app_version>]

So if you want to run 3 tasks with 8 cores each your app_config should look something like this.

<app_config>
<app>
<name>milkyway_nbody</name>
<max_concurrent>3</max_concurrent>
</app>
<app_version>
<app_name>milkyway_nbody</app_name>
<plan_class>mt</plan_class>
<cmdline>--nthreads 8</cmdline>
</app_version>
</app_config>

The --nthreads parameter is the actual controller of how many cpu threads are utilized per each task.
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Message boards : News : New Runs for MilkyWay@home Nbody Simulations (07/29/2020)

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