Re: Quick fix for drix

[Matt Newville <newville@cars.uchicago.edu>]

I don't know if this is exactly relevent, but I definitely saw
a substantial improvement in performance for 100++ paths EXAFS
calculations in Feff7 when I saved the first 30 unique dri()
matrices that were seen.  Like, dri() for single scattering
ought to be calculated once and stored.  For most crystals, the
next ten or so most common angles show up a lot, so saving
O(10) rot matrices was definitely worth it.

That was just a brute force saving dri()  and looking whether
it had been saved before. I'm sure you can come up with
something more clever.

Do you really need to rely on crystalline symmetry? (And
doesn't Si have 1 atom per unit cell?)  I'd think you want to
keep a cluster approach, and let the program determine which
rotation matrices to save.

>   One can probably generate the lookup table for a given
> structure by looping over a given cluster, so no explicit
> symmetry declaration is required. In cases where there is
> large disorder, all pairs will be inequivalent and no
> savings are obtained. However, for cases of disorder, there

Except that beta=180, eta=0 shows up a lot even in all systems.
I'd guessd several other ( beta= 0, eta=0 / beta=120, eta=0 /
...) would show up a lot too.

--Matt