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Old 2020-09-22, 08:52   #1
phillipsjk
 
Nov 2019

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Question My slowest computer was chosen for CERT work

According to https://www.mersenne.org/worktypes/ this page, CERT work is handed out to "reliable computers".


I looked at the exponent's (997xxxxx) status page, and the result I am to certify appears to be composite (C-PRP).


My CPUs are memory bandwidth limited, and the worker it got assigned to won't complete it's current work for 74 days.


If you want the result within the next 6 months, I can move my "workers" around such that I dedicate 1 entire (4 core) CPU+memory bandwidth to the task in the next week or so.


If you want the result within 3 months, I should probably either turn down the work or move it to a faster machine (currently only rated 0.99 reliable, confidence 7.0 -- the one chosen for CERT work is 1.00, confidence 6.0).


Edit: Wait; is the certification a lot less work than the initial test? My computer may be OK with it if that is the case.

Last fiddled with by phillipsjk on 2020-09-22 at 08:59
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Old 2020-09-22, 11:19   #2
ATH
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Yeah, that is the whole idea behind the certificates. They can be proven with about 0.4% of the work of a full test. Around 390.000 iterations instead of 99M
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Old 2020-09-22, 16:25   #3
phillipsjk
 
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I was also worried the work was wanted quickly (as it would be if a new prime was found).


But I gather that it is the equivalent to double-check work.
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Old 2020-09-22, 16:33   #4
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Easiest way to handle it is just let it run. Prime95 will prioritize the CERT work, moving it ahead of the other work without too much delay.
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Old 2020-09-22, 20:19   #5
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Looks like it did get moved to the front of the queue. Should be finished in less than an hour.


Apparently by default up to 10% of your CPU time is devoted to CERT work (but available CERT work is expected to be the limiting factor).
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Old 2020-09-23, 08:41   #6
LaurV
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Yep, CERTs jump the queue. You may be able to change this behavior (read the thread about the new P95) or completely opt out from CERTs, but as long as you opted in, you will get this type of work occasionally, which will "push" or "extend" the time your other tasks will take (PRP, P-1, etc). Running CERTs from time to time is good for your computer, they don't take much time to run, and they check the "sanity" of your hardware (when the verification is successful, you know that your computer runs at least as well as the computer of the other guy who produced the cert )

Last fiddled with by LaurV on 2020-09-23 at 08:42
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Old 2020-09-23, 10:34   #7
phillipsjk
 
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Quote:
Originally Posted by LaurV View Post
Running CERTs from time to time is good for your computer, they don't take much time to run, and they check the "sanity" of your hardware (when the verification is successful, you know that your computer runs at least as well as the computer of the other guy who produced the cert )

All of my machines running mprime have ECC RAM. In theory I should get error messages logged somewhere if my memory is failing. Server-grade hardware is power-hungry though.


My slow machine is mainly doing "strategic" (in the 85xxxxxx range) double-check work anyway. It is not fast enough to do larger (run time too long) or smaller (deadline too short) exponents.


Not sure what the time-frame is, but I think more than 10% of my CPU may be going to CERT work at the moment (with 3 workers the cut-off would be around 8 hours/day). Had 3 jobs in as many days. And the current one is running longer than 8 hours (one was very short due to a cofactor being found).
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Old 2020-09-24, 10:31   #8
LaurV
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Quote:
Originally Posted by phillipsjk View Post
All of my machines running mprime have ECC RAM.
ECC RAM make you feel more comfortable about the fact that whatever you put in the memory stays there unchanged. If you put garbage there, ECC RAM is no help.
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