Procedure

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

Abstract

 
   For those times when we can't do better, we use a bisection 
   method to find the next time at which to test for state change. 
 

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         One of two abscissa values (usually times)
              bracketing a state change. 
 
   t2         The other abscissa value that brackets a state change. 
 
   s1         System state at t1. This argument is provided
              for forward compatibility; it's not currently used.

   s2         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

 
   No errors are returned by this routine. 
 

Literature_References

 
   None. 
 

Author_and_Institution

 
   N.J. Bachman   (JPL)
   W.L. Taber     (JPL) 
   I.M. Underwood (JPL) 
   L.S. Elson     (JPL)
   E.D. Wright    (JPL) 
 

Version

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

Index_Entries

 
   GF standard step refinement
 

Link to routine gfrefn_c source file gfrefn_c.c