Re: OpenGL

[A J Stiles <deb64@earthshod.co.uk>]

On Thursday 06 July 2006 15:42, Francesco Pietra wrote:
> Thanks a lot for this general lesson. That it runs on RedHat was reported
> to me from the author of the application. What I'll try is to recompile the
> application at full 64bit as the companion one above (which was easier
> because of no graphics) I have to ask for the latest source, which was
> recently improved to deal with mpqc.

That's definitely The Proper Way, and will alert you to any potential 
problems.  Hopefully it will all Just Work.

> As indicated in my previous mail (which did not reach you at the time you
> wrote) is to clean from 32bit lib. Please have a look at that mail. You may
> ask why to purge from all 32lib (except grub): I fear that on compiling
> programs that I need for computation - and where the floating point is of
> utmost importance - end not at the best.

I don't think having the 32-bit libraries on your 64-bit system will do any 
real harm, apart from maybe using up a little disk space.  It's what all the 
other Linux distributions  (e.g. Fedora, Mandriva, Gentoo)  seem to do.  If 
you're that bothered, just put all the 32-bit stuff on a physically separate 
drive.  If you've enough RAM then the program and all its libraries will be 
run from there, requiring only one disk access when it is first invoked.

As long as your machine architecture is set up correctly, then anything you 
compile yourself or install from a .deb package should come out as 64-bit; 
you can verify this using ldd, if you're paranoid.

> At any event, I understand that there is a limit for programs not conceived
> for parallel machines. The impressive boost I observed for mpqc from a
> simple Athlon to the multicore amd64 was not observed for the above
> compilation, albeit correct at 64bit. It runs faster on the multicore than
> on the Athlon pc, but not so much.

There's *always* a limit to what can be parallelised and what must be done 
sequentially.  Think of it like this:  Having sex with nine people certainly 
won't get you a baby in one month!

-- 
AJS
delta echo bravo six four at earthshod dot co dot uk