********> bugfix 2.
Author: Andreas Svrcek-Seiler, Niel Michael Henriksen, Scott Brozell,
        reported by Claudio Carra
Date:   8 August 2008

Programs: nab

Severity: major for frcmod.parmbsc0

Description:  The symptom is that NAB terminates with a failed assertion:
sff2.c:1349: ephi2: Assertion `fabs(3.14159 - Phase[atyp]) < 0.01' failed.
The problem is outdated code that validates dihedral phases in prmtop
files.  The patch below allows dihedral phases that are not integral
multiples of pi.  Such dihedral phases are used in the "Barcelona"
changes to ff99 for nucleic acids which is most commonly accessed via
leaprc.ff99bsc0.

Fix:  Apply the following fix to amber10/src/nab/sff2.c

---------------------------------------------------------------------------
*** src/nab/sff2.c	30 Jul 2008 22:15:13 -0000	10.2
--- src/nab/sff2.c	11 Aug 2008 10:42:59 -0000	10.3
***************
*** 1342,1353 ****
           exit(1);
        }
  
!       if (Phase[atyp] == 0.0) {
!          arg = Pk[atyp];
!       } else {
!          arg = -Pk[atyp];
!          assert(fabs(3.14159 - Phase[atyp]) < 0.01);
!       }
  
        e = Pk[atyp] + arg * e;
        df = df * arg;
--- 1342,1351 ----
           exit(1);
        }
  
!       if (fabs(Phase[atyp] - 3.142) < 0.01)
!          arg = -Pk[atyp];
!       else
!          arg = Pk[atyp];
  
        e = Pk[atyp] + arg * e;
        df = df * arg;
---------------------------------------------------------------------------
Workarounds:  none.