AMBER Archive (2008)

Subject: AMBER: Ewald troubles when running very big boxes

From: steinbrt_at_rci.rutgers.edu
Date: Mon Nov 24 2008 - 14:50:50 CST

Hi Amber community,

in trying to simulate a rather large and elongated system (50x50x1000 A) I
ran into the following problems when executing sander:

First:

nfft1-3 too large! check on MAXNFFT in ew_bspline.f

and second:

 Ewald PARAMETER RANGE CHECKING:
 parameter c: (unit cell size) has value 0.10224E+04
 This is outside the legal range
 Lower limit: 0.10000E+01 Upper limit: 0.10000E+04
 Check ew_legal.h

both are connected to the unusually long and big box. When I made the
changes suggested (increasing maxnfft to 1200 and boxhi to 2000) and
recompiled, my calculations appear to run fine.

My question is, has anyone experimented with this before and wants to warn
me about problems that might occur? Specifically, are the various Ewald
maximum size parameters there for a reason or leftovers from a time when
array sizes where just set to a value that seemed large enough?

Thanks in advance,

Kind Regards,

Thomas

Dr. Thomas Steinbrecher
BioMaps Institute
Rutgers University
610 Taylor Rd.
Piscataway, NJ 08854
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