The search up to 10^20

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Allen Paschke

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Message 1242 - Posted: 24 Oct 2019, 18:39:01 UTC - in response to Message 1237.  

Just had a second task with a "Computation Error", when the task was restarted after BOINC decided to run something else --- 15% completed.
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Kellen

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Message 1243 - Posted: 24 Oct 2019, 22:32:40 UTC - in response to Message 1242.  

Hi Allen,

I have found that suspending tasks and restarting them often leads to errors for this project in the past, so I recommend just letting all tasks run to completion when at all possible. Due to the nature of this search it is likely very difficult to implement a reliable checkpoint system without the checkpoints being extremely large (several GB), holding a huge amount of data in RAM (also several GB), or requiring re-initialization of the prime tables (a minute or two) upon resuming calculation.

I know this doesn't really solve the problem, but it is the best advice I can give.

Regards,
Kellen
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bluestang

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Message 1244 - Posted: 25 Oct 2019, 2:41:39 UTC

Would be really nice to be able to run a a multi-GPU system without a large amount of RAM. Trying to run 2x GPUs in a system with 8 or 16GB of RAM is practically impossible with these new 10^21 WUs taking about 8GB of RAM for a single WU.
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Sergei Chernykh
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Message 1245 - Posted: 25 Oct 2019, 5:34:02 UTC - in response to Message 1244.  

It doesn't require 8 GB all the time, you could increase your swap file and be fine with ~1.5 GB physical RAM per task. Now I'm not sure how to make BOINC run with more memory used than available.
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bluestang

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Message 1247 - Posted: 25 Oct 2019, 14:37:19 UTC - in response to Message 1245.  

Ok, thanks for that info. I'll give it a shot and see how it goes.
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Profile PDW

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Message 1249 - Posted: 25 Oct 2019, 17:41:40 UTC - in response to Message 1245.  

It doesn't require 8 GB all the time, you could increase your swap file and be fine with ~1.5 GB physical RAM per task. Now I'm not sure how to make BOINC run with more memory used than available.

On mine a GPU task takes about a minute to get up to near the 8Gb system memory being used and that does not get released until the task completes.
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Sergei Chernykh
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Message 1250 - Posted: 25 Oct 2019, 19:50:08 UTC - in response to Message 1249.  

I repeat: these 8 GB can mostly go into swap file without hurting performance. You don't need physical 8 GB RAM per task, OS will swap out unused parts of memory if you have not enough RAM.
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Kellen

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Message 1251 - Posted: 25 Oct 2019, 20:43:01 UTC - in response to Message 1250.  

I repeat: these 8 GB can mostly go into swap file without hurting performance. You don't need physical 8 GB RAM per task, OS will swap out unused parts of memory if you have not enough RAM.


BOINC won't allow the memory usage to get high enough for the OS to do this unless the Memory settings in the Computing preferences Options window are set very high. I am not sure how high they would need to be set, but I think that the issue people are having is that BOINC will suspend a running task when the memory usage goes above a certain threshold. I think that the default is 50%, but I have mine set at 95% and right now my physical memory usage is 80% with little to no page file usage. Lowering the memory usage percentages just results in suspended tasks on my computer (Windows 10, BOINC version 7.8.3). Ultimately I believe this to be a BOINC issue and not a Windows or Amicable Numbers issue.

To fix it people could try setting the memory usage to 100% and seeing what happens when another task begins running. It could work, but it could also result in a suspended task or a crash of some sort. I'm not brave enough to try in case I break something :)
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bluestang

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Message 1254 - Posted: 26 Oct 2019, 0:40:25 UTC
Last modified: 26 Oct 2019, 0:51:02 UTC

On one of my older machines that has an Intel i7-2600K@4.0GHz and 8GB RAM on W10 Pro it is running 2x 1660ti @ 1 task per GPU. I set my virtual memory on my SSD to 16GB min-24GB max so I don't get Computational Errors. System Manged virtual memory couldn't handle it properly on this machine.

In BOINC 7.14.2 once it gets the first 1m the percentage starts counting, then after about 5 more seconds the percent resets back to 0 and continues as normal. I noticed extreme system lag when it get close to that first 1m mark and also at the end. No biggie except it my home PC, but if I or the wife needs to do something I will suspend BOINC for the duration.
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Kellen

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Message 1257 - Posted: 26 Oct 2019, 2:35:09 UTC - in response to Message 1254.  

Nice workaround! Hopefully that does the trick for everyone else who is having problems too. It does seem like BOINC and Windows can't handle the virtual memory on their own, so I am glad there is another option.
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dannyridel
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Message 1258 - Posted: 26 Oct 2019, 2:38:27 UTC

I've always tried running amicable tasks with the GPU. Somehow they progressed slower and slower as the task goes and eventually they stop running. I discontinued the effort due to a large number of those 'failed' tasks in AUgust. I WONDER IF THIS WAS A PROBLEM IN THE 10^20 app or it also happens in the 10^21 app?
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Kellen

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Message 1264 - Posted: 27 Oct 2019, 2:07:13 UTC

Hi Sergei, I've noticed that there are 8 perpetually unsent tasks for 1020. Anything special with those? I can't seem to grab them and it looks like no one else is getting them either.
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Sergei Chernykh
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Message 1265 - Posted: 27 Oct 2019, 7:48:57 UTC - in response to Message 1264.  
Last modified: 27 Oct 2019, 8:33:13 UTC

I think it's different tasks every time. Some 1020 tasks time out after 3 days, new tasks are created, sent and it repeats.

P.S. I was wrong, these tasks were stuck.
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Kellen

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Message 1266 - Posted: 27 Oct 2019, 12:14:27 UTC - in response to Message 1265.  

Glad to see them out for processing now and even happier to see that you've initiated the accelerated cleanup protocol! The remaining workunits for 1020 should go pretty quick now :)
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Kellen

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Message 1285 - Posted: 1 Nov 2019, 1:37:29 UTC - in response to Message 1266.  

Hi Sergei,

The 1020 stats are gone from the Server Status page. Is the search to 1020 officially complete now?

Thank you,
Kellen
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Sergei Chernykh
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Message 1286 - Posted: 1 Nov 2019, 6:31:30 UTC - in response to Message 1285.  

Yes, it's complete. All previously known amicable numbers were found by the search (which was expected), and many new amicable numbers were found.
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Kellen

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Message 1287 - Posted: 1 Nov 2019, 12:03:17 UTC - in response to Message 1286.  

Fantastic! That is quite the achievement. Congratulations to both yourself, Sergei, for organizing and operating this project, and to everyone who participated!
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mardou123
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Message 1302 - Posted: 14 Nov 2019, 3:51:16 UTC

It is a very happy thing to be able to make some contribution to human development.
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