Procedure

     SHELLD ( Shell sort a double precision array )

     SUBROUTINE SHELLD ( NDIM, ARRAY )

Abstract

     Sort a double precision array using the Shell Sort algorithm.

Required_Reading

     None.

Keywords

     ARRAY
     SORT

Declarations

     IMPLICIT NONE

     INTEGER            NDIM
     DOUBLE PRECISION   ARRAY ( * )

Brief_I/O

     VARIABLE  I/O  DESCRIPTION
     --------  ---  --------------------------------------------------
     NDIM       I   Dimension of the array.
     ARRAY     I-O  The array.

Detailed_Input

     NDIM     is the number of elements in the array to be sorted.

     ARRAY    on input, is the array to be sorted.

Detailed_Output

     ARRAY    on output, contains the same elements, sorted
              in increasing order. The actual sorting is done
              in place in ARRAY.

Parameters

     None.

Exceptions

     Error free.

     1)  If NDIM < 2, this routine does not modify the array.

Files

     None.

Particulars

     The Shell Sort Algorithm is well known.

Examples

     Let ARRAY contain the following elements:

           99.D0
           33.D0
           55.D0
           44.D0
          -77.D0
           66.D0

     Then after a call to SHELLD, the array would be ordered as
     follows:

          -77.D0
           33.D0
           44.D0
           55.D0
           66.D0
           99.D0

Restrictions

     None.

Literature_References

     None.

Author_and_Institution

     J. Diaz del Rio    (ODC Space)
     W.L. Taber         (JPL)
     I.M. Underwood     (JPL)

Version

    SPICELIB Version 1.1.0, 02-JUN-2021 (JDR)

        Added IMPLICIT NONE statement.

        Edited the header to comply with NAIF standard.

        Added entry #1 in $Exceptions section.

    SPICELIB Version 1.0.1, 10-MAR-1992 (WLT)

        Comment section for permuted index source lines was added
        following the header.

    SPICELIB Version 1.0.0, 31-JAN-1990 (IMU)