AMBER Archive (2008)

Subject: RE: AMBER: NAB conjgrad returns error?

From: Andreas Svrcek-Seiler (
Date: Fri Aug 08 2008 - 10:48:28 CDT

Hi again,
first, note the error does not occur inside conjgrad(), but during
NR-minimization when the 2nd derivative version of the force field is

> Subject: RE: AMBER: NAB conjgrad returns error?
> Hey Claudio,
> > run.x: sff2.c:1349: ephi2: Assertion `fabs(3.14159 - Phase[atyp]) < 0.01' failed.
> I have been trouble-shooting the exact same problem. The problem appears to be related to the bsc0 parameters used to build the prmtop file. bsc0 allows for non-integer*pi values for the DIHEDRAL PHASE in the prmtop. You'll find if you make the prmtop using an older force field (i used ff99SB) you won't get the error. I suspect there will have to be some tweaks to the code to resolve this issue.
...This is quite a thorough analysis. Anyway, I have attached a fixed(?)
version of sff2.c. Please try it and let me know whether everything works
For me, all nab-test cases as well as Clausio's script work now.

good luck,

  • APPLICATION/octet-stream attachment: sff2.c.gz
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