Message boards :
Number crunching :
Rounding in app.config (revsited?)
Message board moderation
Author | Message |
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Bill G Send message Joined: 1 Jun 01 Posts: 1282 Credit: 187,688,550 RAC: 182 |
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. SETI@home classic workunits 4,019 SETI@home classic CPU time 34,348 hours |
rob smith Send message Joined: 7 Mar 03 Posts: 22160 Credit: 416,307,556 RAC: 380 |
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 Bob Smith Member of Seti PIPPS (Pluto is a Planet Protest Society) Somewhere in the (un)known Universe? |
Bill G Send message Joined: 1 Jun 01 Posts: 1282 Credit: 187,688,550 RAC: 182 |
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. SETI@home classic workunits 4,019 SETI@home classic CPU time 34,348 hours |
rob smith Send message Joined: 7 Mar 03 Posts: 22160 Credit: 416,307,556 RAC: 380 |
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. Bob Smith Member of Seti PIPPS (Pluto is a Planet Protest Society) Somewhere in the (un)known Universe? |
Bill G Send message Joined: 1 Jun 01 Posts: 1282 Credit: 187,688,550 RAC: 182 |
OK I think I understand. SETI@home classic workunits 4,019 SETI@home classic CPU time 34,348 hours |
BilBg Send message Joined: 27 May 07 Posts: 3720 Credit: 9,385,827 RAC: 0 |
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 Â - ALF - "Find out what you don't do well ..... then don't do it!" :) Â |
Bill G Send message Joined: 1 Jun 01 Posts: 1282 Credit: 187,688,550 RAC: 182 |
Thanks, makes sense now to me....no rounding. SETI@home classic workunits 4,019 SETI@home classic CPU time 34,348 hours |
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