LHC@home

Hi!
I saw that LHC isn't availabl for MacOSX because of a compiler problem. Can't LHC be compiled with G95, http://g95.sourceforge.net/, for MacOSX? It seems to be doing quite well now.

The CERN team have been through a number of iterations with compilers. The underlying problem is with SixTrack's sensitivity to small numerical differences, where even a difference in bit 0 on certain maths function can alter the result substantially over the entire calculation. Early in the project this caused significant headaches where Intel and AMD processors differed in their results.

Yes, the G95 compiler could be used, but without extensive testing there's no guarantee that the numerical results from the Apple platform would match those from the now trusted Intel/AMD application.

CERn has changed the maths library to achieve this consistency. It has been suggested that they are now looking at using GNU compliers, and if this works they might consider an Apple version.

However, this will take time, and given that the regular team on LHC@Home numbers about half a full time person spread between three individuals with other responsibilities, I wouldn't expect any news any time soon...

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Gaspode the UnDressed
http://www.littlevale.co.uk

Developing and managing computational projects wtih too litle time to do it is something I've had my own share of too so I'm certainly not complaining her, just being curious. As long as one doesn't contribute to the coding one don't really have the right to complain much.

Having this kind of machine dependency is something that is quite different from my own work, where any variation at all can't be tolerated. Given that there seems to be quite a lot of people who wants to run LHC it might be worth changing to a numerical library which does everything in machine independent way, at the cost of slowing things down a bit. But I realise that this might need a LOT of rewriting of nontrivial code.

I like the project, maybe we'll see an ITER@home in a few years time too.

Pardon my ignorance, but where might I have found out that there was no Mac client software for this project before going through the trouble of signing up?

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> Pardon my ignorance, but where might I have found out that there was no Mac
> client software for this project before going through the trouble of signing
> up?

The "Apps" page. there is usually a link to it off of the accunt set-up pages. There are tables in the Wiki too ...

if there is not a direct link, just take the normal part of the web address and add "apps.php" and that will get you home ...

The other projects, for the most part have OS-X apps ... though the CPDN app always crashes on my PowerMac G5 ... so, I don't know what is going on there ...

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> I like the project, maybe we'll see an ITER@home in a few years time too.
>

enlighten me. what is ITER@home?

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> > I like the project, maybe we'll see an ITER@home in a few years time
> too.
> >
>
> enlighten me. what is ITER@home?
>

ITER is the name for the new experimental fusion reactor to be built in France over the next few years. It is supposed to be the first such reactor that will produce more energy than it consumes.

ITER@Home is the speculative name for a DC project that could possibly be be put in place to support the build. I stress 'speculative', since as far as I know there is no such project, nor any plans for one at this time.

See http://www.iter.org for more info.

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Gaspode the UnDressed
http://www.littlevale.co.uk

I understood the speculative nature of the name when I asked. Thank you for the information. I will have to look at this site. It looks very interesting. I wish the people here in the US would accept alternative fuels for generating stations. Sheesh.

Jim

> ITER is the name for the new experimental fusion reactor to be built in France
> over the next few years. It is supposed to be the first such reactor that will
> produce more energy than it consumes.
>
> ITER@Home is the speculative name for a DC project that could possibly be be
> put in place to support the build. I stress 'speculative', since as far as I
> know there is no such project, nor any plans for one at this time.
>
> See http://www.iter.org for more info.
>
>

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Yes I am not avare of any such DC project either. However using this approach to help fiding the correct starting points for machines like LHC and ITER will probably grow more and more common.

Another future candidate for simulation tuning which is closer to LHC might be its planned sibling the International Linear Collider, which is still on the drawing board.
ILC

That link doesn't work, try this one.

> That link doesn't work, try <A> HREF="http://www.interactions.org/linearcollider/"> this one[/url].
>

Oops - my mistake. Try this (corrected) version: http://www.iter.org

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Gaspode the UnDressed
http://www.littlevale.co.uk