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Re: CIF development strategies

• Subject: Re: CIF development strategies
• From: Louis Farrugia <louis@xxxxxxxxxxxxxx>
• Date: Fri, 5 May 2000 17:34:54 +0100 (BST)

Dear Brian

>> Like PLATON, SHORTEP places a few restrictions on the order of items
>> in the CIF -- specifically that the atom type symbols come before
>> the atoms and that the atoms come before the thermal parameters or in
>> the same loop with them.  These restrictions permit SHORTEP to read
>> and process a CIF in one pass, without storing any unnecessary data
>> in memory or scratch space.  The approach does not require the overhead
>> of a large (albeit rigorous) API like CIFtbx, yet is still flexible and
>> extensible.
>
>Do you suffer a real performance hit by hooking in CIFtbx routines to
>reorder your input data? I'm just curious, because it seems a pity to
>impose order dependence - the application is then unable to read any
>arbitrary CIF. To my mind that need not be considered as completely
>devaluing the application; on a Unix box it's easy enough to knock up
>a script using a standalone utility (such as the great-grandaddy
>of them all, QUASAR) to pre-order your input. Nevertheless, it does 
>seem to hobble it a bit.
>
>Is there a need for a lightweight subroutine library to input data in
>a specific order? Is that achievable in Fortran in any more efficient way
>than CIFtbx?

I used CIFtbx in a Fortan environment specifically because I did not wish
to impose
such restrictions. The later versions of CIFtbx have substantial memory
requirements 
but I cannot say I have noticed performance degradation. However in their
present form
they routines suffer from one minor inconvenience in that the applications
which use this API
usually need to get direct access to the memory store (i.e. the common
blocks). This make is more difficult to use CIFtbx as a DLL (Windows) or as
a run-time libraries(UNIX) or in a mixed Fortran-C application. I believe
there is a C version of CIFtbx somewhere ?? though I havent investigated  this
  
Louis Farrugia
=====================================================================
From:
Dr. Louis J. Farrugia
Department of Chemistry
University of Glasgow,
GLASGOW G12 8QQ
Scotland, UK.

Phone:  +44 (0)141 330 5137
FAX:    +44 (0)141 330 4888
email:  louis@chem.gla.ac.uk
Web  :  http://www.chem.gla.ac.uk/~louis/
=====================================================================

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