[cctbxbb] Documentation on caching mechanisms implemented in structure factor calculation

Jan M. Simons marten at ifk.rwth-aachen.de
Mon Sep 28 10:07:34 PDT 2020

Hello fellow researchers and scientists,

It's been a while since I actively worked with cctbx, but now I wonder
if there is some in depth documentation on how the structure factor
calculation in the cctbx xray module is done. I'm especially interested
in caching strategies employed to speed up the calculation during
refinement runs (especially in the case of small molecules using direct

So is there a kind of caching that keeps (partial) structure factor
contributions of each individual scatterer cached so that only the
partials of shifted scatterers have to be recalculated? If so is there a
python interface for accessing those?

Also is there an option to simulate/map the f_calc amplitudes onto a
1dimensional 2theta or d* axis to compare those to powder diffraction

Thanks in advance for giving me some guidance on this (especially if
there have been some recent additions to these modules).


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