Rounding in app.config (revsited?)

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Message 1760750 - Posted: 30 Jan 2016, 15:41:09 UTC
Last modified: 30 Jan 2016, 15:42:16 UTC

I have been playing around with CPU usage in my app.config, trying to keep my GPU properly busy. I had a rare opportunity to be running 3 WUs and 1 AP and noticed that I had my CPU usage set to .33 for the WUs. While the three were running they were not reserving a core. Realizing that .33 X 3 is .99 it seems you have to set the CPU to .34 so that 3 WUs will reserve a core.
As I said this may have been discussed before, just my observation.

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Message 1760807 - Posted: 30 Jan 2016, 18:22:33 UTC - in response to Message 1760750.  

It is safer to set 0.33 as 0.34 will lead to an over-commitment, and instead of reserving one core you might actually block two
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Message 1760823 - Posted: 30 Jan 2016, 19:27:59 UTC - in response to Message 1760807.  

What was happening was a full core was not being assigned when it was .33 and only 3 WUs were running.
What I had was one core for the AP and what I wanted was a full core the 3 WUs running at the same time, or is that really what I do not want?

Same general subject: Can you tell from the amount of CPU being used whether you have assigned enough? I tried 2 cores for the AP and it only used .49 of that, or one core. So I assumed that 1 core was correct for the V7 AP.

I thought I had read that if your CPU is sitting at 100% usage that that is not a good thing. I have been trying to have a bit of extra CPU in reserve.

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Message 1760830 - Posted: 30 Jan 2016, 19:52:26 UTC

It is not imperative that a complete core is used, as SETI will use what it needs up to the maximum number of complete cores reserved - and 0.01 cores counts as one core.
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Message 1760850 - Posted: 30 Jan 2016, 20:28:13 UTC - in response to Message 1760830.  

OK I think I understand.

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Message 1761282 - Posted: 1 Feb 2016, 10:06:13 UTC - in response to Message 1760750.  

Realizing that .33 X 3 is .99 it seems you have to set the CPU to .34 so that 3 WUs will reserve a core.

Yes, it is the way it works (unless there is some newer BOINC code I don't know about)
BOINC do not do "Rounding" - it Truncates, try with 0.66 and you'll have to see the math is:
0.66 * 3 = 1.98 = 1

i.e. BOINC will "reserve" 1 core even if you use 0.66
 


- ALF - "Find out what you don't do well ..... then don't do it!" :)
 
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Message 1761322 - Posted: 1 Feb 2016, 14:57:43 UTC - in response to Message 1761282.  

Thanks, makes sense now to me....no rounding.

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Message boards : Number crunching : Rounding in app.config (revsited?)


 
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