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Jython, GILs and object locking.

John J. Lee jjl at pobox.com
Sat Oct 11 16:01:20 EDT 2003 
"Andrew Dalke" <adalke at mindspring.com> writes:
[...]
> I don't know anywhere near enough about the theory, but my
> understanding is that it computes a huge number of integrals, and
> the results of these calculations are used enough times that it's better
> to cache and reuse a result then it is to recompute the value.

Yes [way off topic, but who cares...], AAUI (which is to say, hardly
at all ;-) it uses a neat mathematical trick, treating the electronic
changes as if they were in some sense just motion along more nuclear
coordinates, to get away without having to do a DFT calculation for
every 'frame' (time slice) of the simulation.


> "huge" means back in the early to mid-90s when someone in
> my group needed to do a QC job, they had to get him a 1 Gig
> drive just as scratch space for the cache.

I guess that was before beowulf machines became popular and when
typical RAM sizes were much smaller.  Of course, things move on, of
course: a year or two ago, the 1 Gb of RAM in each of the machines was
described to me as 'only 1 Gb', and there were maybe five AMD machines
there -- so it was the network that required most attention (some
fibre-optic thingy, I think).


John
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