SFALL Bug

["Borhani, David" <borhani@sri.org>]

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Dear All,

There is an insidious bug in SFALL.

If you give the program an MTZ file that has the correct symmetry and cell
dimensions in the MTZ header, as well as a PDB file that does not have
CRYST1 cards, the program runs, does NOT complain, and calculates an
absolutely wrong answer (apparently, it assumes that the cell is
1,1,1,90,90,90).

If you give SFALL the SYMMETRY and CELL cards on the command line, this bug
does not occur. (This is paradoxical behaviour, and wrong, in my opinion).

If you run SFALL as recommended in the documentation, i.e. with a PDB file
that HAS the CRYST1 cards (and do not give the SYMMETRY and CELL cards on
the command line), all is OK as well.

The documentation states that it is "ESSENTIAL" that the PDB file have the
CRYST1 cards, yet the program does not warn you if they are missing.

My suggestions:

1. Fix the "feature/bug", so that if valid cell & symmetry are present in
the MTZ file, then a PDB file without CRYST1 cards will work correctly,
perhaps with a clear warning that the cell & symmetry are being drawn from
the MTZ file, and that it is being assumed that the PDB file is in the
standard orientation (NCODE=1).

2. Alternatively, have SFALL come to a GRINDING HALT if it reads a PDB file
without the CRYST1 cards, with lots of warning as to why it stopped. (This
will save a lot of time trying to figure out why your Fc's don't scale to
Fo's!). 

3. Change the documentation.

 Thanks

David Borhani                   borhani@sri.org
Southern Research Institute     Tel: (205) 581-2555
2000 Ninth Avenue South         Fax: (205) 581-2877
Birmingham, AL 35205 U.S.A.