LHC@home

Hi Folks,
having read through many other threads without success. I'm afraid I have to open one more on this issue.
How to understand the various parameters, that can be set in the preferences menues for the best share of performance ?
My first problem is the understanding of some of the parameters in the general BIONIC settings:
a- On multiprocessors, use at most x processors
b- On multiprocessors, use at most x % of the processors
c- Use at most x % of CPU time.

Point a- seems to be clear: you can tell how many of your Quad Core CPUs shall be used (1, 2 or 3).
Point b could then mean to allow the max load on those given in point a (maybe 50% on each of the three I did select).
Point c is then really confusing: Is this now the average percentage of the Quad CPU ? Do I have to calculate that ( three out of four at 50%) ?

Finally I got totally lost when I found the parameter in the preference menue of the SIXTRACK project asking for:
d- Max CPU for gaphics...40
Is this a typo and should read GPU ? And if not, what is it asking for: 40 %(?) of what ? And why ?
What should I enter ?

I'm using an Intel Dual Core @2.6 GHz with a GeForce 8800GT, which is not brand new but should provide enough spare capacity for number crunching when doing just some office stuff.

I'm really interested to support your project and I feel I could do better if I don't use the standart settings.

Kind regards,
Flatlander.

The settings are a bit confusing. a and b refer to the the number of cores/processors you allow BOINC to use. If you have a 4 core i7 with hyper threading enabled BOINC will see 8 cores. If you set a to 8 BOINC will use all 8. If you set a to 5 BOINC will use 5. If you set b to 100% BOINC will use 8. If you set b to 25% BOINC will use 2. I use the local settings rather than the website settings (click Tools -> Computing Preferernces -> CPU Usage) and those settings do not include item a, just b. I don't know why the website has a. If you use the local settings then they will override the website settings.

Item c determines how many of your spare CPU cycles BOINC will use. It's a throttle and it's intended use is to reduce CPU temperatures. At 40%, BOINC will suspend computing for all your projects for 60% of the time and allow computing for 40% of the time. It's a very coarse throttle which operates at the seconds level as opposed to the milliseconds level. At 40%, for example, it will run the tasks for 4 seconds then suspend the tasks for 6 seconds.

Regarding the a and b settings it's actually not correct to say "BOINC will use x cores" but it's become part of the BOINC culture to use that expression. What "will use x cores" actually means is that BOINC will run x single-threaded tasks at a time. How many cores the x tasks actually use is determined by the OS not BOINC. For example, if you have a 4 core CPU and allow BOINC to use only 1 core BOINC will run only 1 task but you may find that task running on 3 or 4 cores not just 1 core.

BTW, the program is called BOINC, not BIONIC. And you will find this project, Sixtrack, does not have a continuous supply of tasks. There are long dry spells where there is no work available. If you are interested in particle physics and would like to help CERN with some LHC related work then consider joining Sixtrack's "sister" project Test4Theory@home which has a continuous supply of tasks. Be sure to follow the first few links on the home page to get to the directions for installing VirtualBox. Test4Theory will not run without VirtualBox.