[phenixbb] Speeding direct summation ?
pafonine at lbl.gov
Fri Nov 2 09:38:56 PDT 2018
> I have (very) high resolution data, for which direct summation method
> seems to give significantly better map than FFT (i.e. visible hydrogen
> vs not).
at some point we spent a lot of time experimenting with this:
Acta Cryst. (2004). A60, 19-32
On a fast calculation of structure factors at a subatomic resolution
P. V. Afonine and A. Urzhumtsev
and I can't remember seeing any significant difference in
R-factors/maps. So.. there must be something special going on in your
case. If you send me files I may be able to tell you what exactly is
going on. Otherwise, if you'd like to tackle this yourself, you can
start with changing sampling finess (resolution_factor) to something
like 1./5 or 1/6., which will still be much faster than direct summation
yet produce even greater match between approximations.
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