********> bugfix.49
Author:   Bill Ross
Date:     10/21/95

Programs: Leap

Severity: Moderate

Problem:  Improper torsions in 'parm.dat' or 'frcmod' files: if a 
          value is given for IDIVF (which Parm ignores for 
          impropers), Leap will misread the whole line, shifting 
          values to the wrong variables. Thus the throwaway idivf 
          value would be used for PK (energy), the energy term
          (typically <50) would be used for PHASE instead of the 
          correct phase of 180 degrees for impropers, and the
          phase would be used for PN (periodicity of the torsional 
          barrier).  The effect of this on a simulation is hard to 
          predict, since it depends on the throwaway value used for 
          IDIVF; 0 would be a likely choice, in which case the whole 
          improper term would have no effect.

Affects:  dat/contrib/heme/frcmod.* and possibly user-supplied force 
          field files.  If one is using topology files for which the 
          original parm.dat or frcmod files are unavailable to check, 
          running the .top/.crd files through Anal with the amber41/
          templates/anal.in will fail with a cryptic error like this, 
          assuming 180 was used for the PHASE:

             DIHEDRAL ANGLE ERROR:  132 764 832 829 841     .0175 


Cause:    The original authors of Parm specified an extraneous number
          in the improper torsion term to be consistent with the
          proper torsion term, and the original author of Leap 
          assumed the standard practice of omitting the unused
          number instead of following the spec exactly.

Fix:  Make the following change to amber.c: replace subroutine
      zAmberReadParmSetImpropers() with the following:
----------------------------------------------------------------------
/*
 *	zAmberReadParmSetImpropers
 *
 *	Read the improper torsion parameter terms.
 */
FUNC
void	zAmberReadParmSetImpropers( psParms, fIn )
PARMSET	psParms;
FILE*	fIn;
{
STRING		sLine;
int		iRead;
STRING		saStr[10];
double		dDivisions, dKp, dP0, dN;
int		iN;
BOOL		bPrintLine;
BEGIN
    while (1) {
        FGETS( sLine, fIn );
        NODASHES(sLine);
	/*
	 *  get atoms & values, skipping possible 
	 *	extraneous idivf value allowed by
	 *	the input spec for PARM
	 */
        iRead = sscanf( sLine, "%s %s %s %s",
                                saStr[0], saStr[1], saStr[2], saStr[3] );
        if ( iRead != 4 ) break;
        iRead = sscanf( sLine+15, "%lf %lf %lf", &dKp, &dP0, &dN );
        if ( iRead != 3 ) break;
	MESSAGE(( "Read: %s\n", sLine ));
	dN = (int)floor(dN+0.5);
	zAmberConvertWildCard( saStr[0] );
	zAmberConvertWildCard( saStr[1] );
	zAmberConvertWildCard( saStr[2] );
	zAmberConvertWildCard( saStr[3] );
	iN = (int)dN;

	/*
	 *  check everything in case a format or other user error
	 *	led to wrong values, e.g. IDIVF offset
	 */
	bPrintLine = FALSE;
        if ( dKp <= 0.0 ) {
	    VP0((" WARNING: expected Improper Torsion PK>0 (%f)\n",
		dKp ));
	    bPrintLine = TRUE;
	}
        if ( dP0 < 179.999  ||  dP0 > 180.001 ) {
	    VP0((" WARNING: expected Improper Torsion PHASE=180 (%f)\n",
		dP0 ));
	    bPrintLine = TRUE;
	}
        if ( iN < 1  ||  iN > 6 ) {
	    VP0((" WARNING: unexpected Improper Torsion PN term (%d)\n",
		iN ));
	    bPrintLine = TRUE;
	}
	if ( bPrintLine )
	    VP0(( " Here is the Improper Torsion line in question:\n%s", 
								sLine ));

        iParmSetAddImproperTerm( psParms, 
				saStr[0], saStr[1], saStr[2], saStr[3],
                                iN, dKp, dP0*DEGTORAD, "" );
    }
    if ( iRead > 0 )
	VP0(( "WARNING: incomplete Improper Torsion line:\n%s", sLine ));
END
}

----------------------------------------------------------------------

Temporary workarounds: Replace any numerical values for Improper Torsion 
			IDIVF field with spaces in parm.dat, frcmod files.

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