Questions and Answers : Sixtrack : optimize sixtrack for amd athlon xp
Matthias Nass
Message 9751 - Posted: 31 Aug 2005, 8:41:10 UTC
Is there a way to optimize sixtrack for particular processor Types? i had compiled boinc in Linux with flags for my amd athlon xp and now the benchmark is about 35% faster. But that takes no effect to sixtrack itself. So it would be great to optimize sixtrack.So that the crunch of the wu´s will be faster. Are Fortran Sources be able to compile optimized for diffrent cpu types? Is there a way to do that?
ID: 9751 · Reply Quote
Gaspode the UnDressed
Message 9774 - Posted: 31 Aug 2005, 17:18:16 UTC
Sixtrack is one of the applications used by compiler writers to optimise their compiler output. It is, by default, optimised.
The Fortran code for LHC@Home's SixTrack isn't available and isn't likely to be. There are numerical differences between different compiler implementations and between different families of processor. These differences are small, but in Sixtrack they become significant.
The LHC@Home team have settled on a compiler that gives good results across the range of processors they expect to use. Releasing the source code opens up the possibility of incorrect results being returned and a great deal of work wasted.
This is also the reason why no Mac version exists - the chosen compiler doesn't compile for the Mac platform.
http://www.littlevale.co.uk
Chrulle
Credit: 1,880
Message 9809 - Posted: 1 Sep 2005, 10:06:47 UTC
Very often compiling something with full optimization for a specific platform will give faster run times, but it is using specific architectural quirks that will lead too calculation errors. The same goes for overclocking your cpu, it will make it faster but it will no longer calculate correctly.
Normally this is never a problem. If you play a game and your player character gets calculated a bit wrong. Say 5 mm to left pr hour of game. You will never notice it. If the same error happens in sixtrack a particle may have moved 2-10 cm to the left after the 10 hr. simulation. This would be enough to move it out of the vacuum tube and such an event would be catastrophic. The LHC is actually build with a precision of 1 millimeter. This means that we even have to take the moons gravitational influence into account and we have to adjust for when the TGV drives past in downtown Geneva. So even a very small error in the Sixtrack caclualtion is a problem,
Research Assistant & Ex-LHC@home developer
Niels Bohr Institute
Message 10094 - Posted: 12 Sep 2005, 13:22:04 UTC - in response to Message 9809.
What's a TGV?
ID: 10094 · Reply Quote
Message 10100 - Posted: 12 Sep 2005, 17:12:36 UTC - in response to Message 10094.
<blockquote>What's a TGV?</blockquote>
TGV - Train a Grand Vitesse - literally Very Fast Train. It's the French high speed train that runs the international rail routes and long distance rail routes from Paris to Bordeaux, Marseille, Geneva, Brussels, etc.
It's a measure of the sensitivity of the LHC that the gravitational pull of a couple of hundred tons of train at a distance of a few kilometres has to be taken into account.
Of course, Chrulle's remarks may be a little 'tongue in cheek'
tilad-x
<blockquote><blockquote>What's a TGV?</blockquote>
The amount of electricity used by the TGV can produce a large magnetic field, which can disrupt the path of a single particle several kilometers away by enough to destroy any valuable information which may have been received. Operators and scientists at cyclotrons and particle colliders literally have to anticipate any forseeable event - such as the scheduled TGV and any scheduled commercial flights.