[cctbxbb] Fast way to enable/disable individual scatterers in structure factor calculation

[Luc Bourhis]

On 29 Jun 2012, at 11:47, Jan Marten Simons wrote:

> Am Freitag 29 Juni 2012 10:27:19 schrieb Luc Bourhis:
>> Hi Jan,
>> 
>>> I'm looking for a simple and fast way to set individual scatterers to be
>>> either included or excluded from structure factor calculation.
>> 
>> I recommend not to do that. Instead I would create a new instance of
>> xray.structure with those scatterers you want, using the the methods
>> xxx_selection and then the method select, and then use it for structure
>> factor calculations.
> 
> I'm concerned about overhead here, as I'd like to quickly check a lot (some 
> millions) of different variations of a basically identical structure against a 
> set of given f_obs. I only need to calculate f_calc once for each of the 
> slightly modified structures.
> So I think simply masking one or some of the scatterers instead of creating a 
> new (copy of the) structure would save a huge ammount of cpu time.

The structure factor calculations will typically dwarf the copies.
As usual, try it, time it and if it is too slow then profile it to ascertain where you should spend your time optimising.

Best wishes,

Luc Bourhis