Saturday, December 29, 2012

BOINC: CPU Time vs CPU Utilization

I mentioned I was going to run this experiment awhile back, and while I have been running it, I forgot exactly how my computer initially behaved, so switching a few settings back, I can now give a report on whether it is best to cut back on CPU Utilization or cut back on Percentage of CPU time BOINC uses.

Results:  I have found that in terms of both temperature control, and credits earned in a lengthy amount of time ( lets just say 1 month), that it is better to use all CPU's but throttle back the CPU time.

Hardware: This is on my Dell Laptop running  an Intel i3 Processor with 2 cup's but hyperthreading enabled causing BOINC to view it as 4. Ubuntu 12.04 is my OS.

First set up: Using 50% of the processors, I could only crunch two tasks at once, but it did enable me to crunch projects quicker, as I could increase my CPU utilization to nearly 50% before the temp became unstable ( I like to keep the temp of my CPU below 80C, though at 50% of CPU time it would often flirt above that line, especially if any other task on the computer was running).

Second set up: Using 100% of processors, so I can crunch four tasks at once, in theory this places any stable CPU temps, at a utilization of anywhere over 25% a slight victory.  I recalled 30% being stable in the past, which is why I was keen to try something else, as projects seemed to take forever to complete.  But now ( maybe because it is winter and the temps are in general cooler), I can get stable temperatures while using 35% of CPU time.

If your goal is to finish each task as quickly as possible the second set up is not for you.  But if the goal is to do as much crunching as possible, even if each task does take longer, the second set up seems ideal.  I have not quite thought of an exact way to measure these performance factors, but assuming 50% of CPU's at 50% utilization is identical to 100% of CPU's at 25% utilization, I in theory while running at 35% utilization have a 40% increase in performance over an extended length of time. 

The 40% is calculated, based on CPU time spent on each project.  Two cores, each with 1 project spending 1/2 of every second on a project amounts to 1 second of crunching each second.   While when crunching 4 projects at 35% means each second we advance the combined four projects by 1.4 seconds.  Thus 1.4 is 40% better than 1.

Friday, December 21, 2012

Graphics Cards (if I could dream)

PNY Technologies VCQ4000-PB Quadro 4000 PCIE X16 (Google Affiliate Ad)

I have been reading a lot about graphics cards lately, and comparing oh so many of them.  I have been fighting really hard to resist the urge  to not buy all the parts for a new computer. Of course what graphics card you use really depends on what you will be using the computer for when you are not crunching away.  Maybe because I am a big fan of GPUgrid, when I think graphics cards I think nvidia, and their cuda techonology.  But to make sure it can run other programs too check to make sure it works with OpenGL, ( the more recent the version it supports the better).

Things like the Quadro 4000 are a very nice choice.  Though with a bit more power and a similar outlay of money, a Geforce 690 may be the way to go, double the GPU chips double the fun right?  For a more affordable price you can find PNY Technologies VCQ600-PB Quadro 600 1GB DDR3 PCIe (Google Affiliate Ad)
 which is also on GPU grids recommended list.  Another reason why I mention these are the facts that they have at least 1GB of memory reserved for the card alone.

Of course if I really could dream I would set up a system with 2 if not 3 GPU's which I imagine could replace my furnace, though be just as costly a way to heat my home. 

Again these are just dreams.  But I feel us crunchers always wonder how we can get better and better systems just to help these scientists with their work.

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