[Pw_forum] One minor bug, one not minor and two questions

[Laurence Marks]

A very minor bug that you probably known: some of the routines in
S3DE/iotk/src have lines such as "# 1 "iotk_write_interf.spp" ". Most
sensible preprocessors will ignore these and just give warnings.

A more serious bug. Your bfgs code does not have curvature failure
conditions trapped. Not to get too technical here (contact me offline
if needed), unless one is close to the minimum bfgs fails unless this
is done. The failure is well documented, less well known, as is the
change needed (at least the standard form). I am attaching a modified
version with the standard fix. It gives a slightly lower energy with
smaller forces in about the same number of iterations -- due to
numerical limitations I cannot compare exactly with your reference
directory. I am a newbie with this code so there could be other
repercussions of this change if it is used for something except
optimizing the atomic positions, so perhaps a few tests are
appropriate for harder problems.

A quick question. In the ion optimization it looks like you are
starting from some iterpolation of the new density (i.e. "NEW-OLD
atomic charge density approx. for the potential"), what is it?

Another quick one: line 1766 of install/configure.ac nulls out
scalapack_libs and the lines below look like they are special tests,
which seems to be inconsistent with line 150 and standard protocols of
letting the user define input variables. (OK, while scalapack is
probably only useful for large problems I might want to do some.)

-- 
Professor Laurence Marks
Department of Materials Science and Engineering
MSE Rm 2036 Cook Hall
2220 N Campus Drive
Northwestern University
Evanston, IL 60208, USA
Tel: (847) 491-3996 Fax: (847) 491-7820
email: L-marks at northwestern dot edu
Web: www.numis.northwestern.edu
Chair, Commission on Electron Crystallography of IUCR
www.numis.northwestern.edu/
Research is to see what everybody else has seen, and to think what
nobody else has thought
Albert Szent-Gyorgi
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