Procedure

   gfrefn_c ( GF, default refinement estimator ) 

   void gfrefn_c ( SpiceDouble     t1,
                   SpiceDouble     t2,
                   SpiceBoolean    s1,
                   SpiceBoolean    s2,
                   SpiceDouble   * t  )

Abstract

   Estimate, using a bisection method, the next abscissa value at
   which a state change occurs. This is the default GF refinement
   method.

Required_Reading

   None.

Keywords

   SEARCH
   UTILITY

Brief_I/O

   VARIABLE  I/O  DESCRIPTION
   --------  ---  --------------------------------------------------
   t1         I   One of two values bracketing a state change.
   t2         I   The other value that brackets a state change.
   s1         I   State at `t1'.
   s2         I   State at `t2'.
   t          O   New value at which to check for transition.

Detailed_Input

   t1          is one of two abscissa values (usually times)
               bracketing a state change.

   t2          is the other abscissa value that brackets a state change.

   s1          is the system state at `t1'. This argument is provided
               for forward compatibility; it's not currently used.

   s2          is the system state at `t2'. This argument is provided
               for forward compatibility; it's not currently used.

Detailed_Output

   t           is the midpoint of `t1' and `t2'.

Parameters

   None.

Exceptions

   Error free.

Files

   None.

Particulars

   "Refinement" means reducing the size of a bracketing interval on
   the real line in which a solution is known to lie. In the GF
   setting, the solution is the time of a state transition of a
   binary function.

   This routine supports solving for locations of bracketed state
   transitions by the bisection method. This is the default
   refinement method used by the GF system.

   The argument list of this routine is compatible with the GF
   system's general root finding routine. Refinement routines created
   by users must have the same argument list in order to be used by
   the GF mid-level APIs such as gfocce_c and gffove_c.

Examples

   The following code fragment from an example program in the header of
   gfocce_c shows the address of this routine passed as the 12th argument.

      /.
      Perform the search.
      ./
      gfocce_c ( "ANY",
                 "MOON",     "ellipsoid",  "IAU_MOON",
                 "SUN",      "ellipsoid",  "IAU_SUN",
                 "LT",       "EARTH",      CNVTOL,
                 &gfstep_c,  &gfrefn_c,    rpt,
                 &gfrepi_c,  &gfrepu_c,    &gfrepf_c,
                 bail,       &gfbail_c,    &cnfine,
                 &result                              );

Restrictions

   None.

Literature_References

   None.

Author_and_Institution

   N.J. Bachman        (JPL)
   J. Diaz del Rio     (ODC Space)
   E.D. Wright         (JPL)

Version

   -CSPICE Version 1.0.1, 01-NOV-2021 (JDR)

       Edited the header to comply with NAIF standard.

   -CSPICE Version 1.0.0, 15-APR-2009 (NJB) (EDW)

Index_Entries

   GF standard step refinement