Procedure

     VSUBG ( Vector subtraction, general dimension )

     SUBROUTINE VSUBG ( V1, V2, NDIM, VOUT )

Abstract

     Compute the difference between two double precision vectors of
     arbitrary dimension.

Required_Reading

     None.

Keywords

     VECTOR

Declarations

     IMPLICIT NONE

     INTEGER            NDIM
     DOUBLE PRECISION   V1   ( NDIM )
     DOUBLE PRECISION   V2   ( NDIM )
     DOUBLE PRECISION   VOUT ( NDIM )

Brief_I/O

     VARIABLE  I/O  DESCRIPTION
     --------  ---  --------------------------------------------------
     V1         I   First vector (minuend).
     V2         I   Second vector (subtrahend).
     NDIM       I   Dimension of V1, V2, and VOUT.
     VOUT       O   Difference vector, V1 - V2.

Detailed_Input

     V1       is a double precision vector of arbitrary dimension which
              is the minuend (i.e. first or left-hand member) in the
              vector subtraction.

     V2       is a double precision vector of arbitrary dimension which
              is the subtrahend (i.e. second or right-hand member) in
              the vector subtraction.

     NDIM     is the dimension of V1 and V2 (and VOUT).

Detailed_Output

     VOUT     is a double precision n-dimensional vector which
              represents the vector difference, V1 - V2.

Parameters

     None.

Exceptions

     Error free.

Files

     None.

Particulars

     For each value of the index I from 1 to NDIM, this routine
     performs the following subtraction:

        VOUT(I) = V1(I) - V2(I)

     No error checking is performed to guard against numeric overflow
     or underflow.

Examples

     The numerical results shown for this example may differ across
     platforms. The results depend on the SPICE kernels used as
     input, the compiler and supporting libraries, and the machine
     specific arithmetic implementation.

     1) Define two sets of n-dimensional vectors and compute the
        difference from each vector in first set with the
        corresponding vector in the second set.


        Example code begins here.


              PROGRAM VSUBG_EX1
              IMPLICIT NONE

        C
        C     Local parameters.
        C
              INTEGER               NDIM
              PARAMETER           ( NDIM   = 4 )

              INTEGER               SETSIZ
              PARAMETER           ( SETSIZ = 3 )

        C
        C     Local variables.
        C
              DOUBLE PRECISION      V1   ( NDIM, SETSIZ )
              DOUBLE PRECISION      V2   ( NDIM, SETSIZ )
              DOUBLE PRECISION      VOUT ( NDIM         )

              INTEGER               I
              INTEGER               J

        C
        C     Define the two vector sets.
        C
              DATA                  V1 /
             .                      1.D0,  2.D0,  3.D0,  4.D0,
             .                      1.D0,  2.D0,  3.D0,  4.D0,
             .                      1.D0,  2.D0,  3.D0,  4.D0   /

              DATA                  V2 /
             .                      1.D0,  1.D0,  1.D0,  1.D0,
             .                     -1.D0, -2.D0, -3.D0, -4.D0,
             .                     -1.D0,  2.D0, -3.D0,  4.D0  /

        C
        C     Calculate the difference between each pair of vectors
        C
              DO I=1, SETSIZ

                 CALL VSUBG ( V1(1,I), V2(1,I), NDIM, VOUT )

                 WRITE(*,'(A,4F6.1)') 'First vector : ',
             .                        ( V1(J,I), J=1,NDIM )
                 WRITE(*,'(A,4F6.1)') 'Second vector: ',
             .                        ( V2(J,I), J=1,NDIM )
                 WRITE(*,'(A,4F6.1)') 'Difference   : ', VOUT
                 WRITE(*,*)

              END DO

              END


        When this program was executed on a Mac/Intel/gfortran/64-bit
        platform, the output was:


        First vector :    1.0   2.0   3.0   4.0
        Second vector:    1.0   1.0   1.0   1.0
        Difference   :    0.0   1.0   2.0   3.0

        First vector :    1.0   2.0   3.0   4.0
        Second vector:   -1.0  -2.0  -3.0  -4.0
        Difference   :    2.0   4.0   6.0   8.0

        First vector :    1.0   2.0   3.0   4.0
        Second vector:   -1.0   2.0  -3.0   4.0
        Difference   :    2.0   0.0   6.0   0.0

Restrictions

     1)  No error checking is performed to guard against numeric
         overflow. The programmer is thus required to insure that the
         values in V1 and V2 are reasonable and will not cause
         overflow. No error recovery or reporting scheme is
         incorporated in this routine.

Literature_References

     None.

Author_and_Institution

     N.J. Bachman       (JPL)
     J. Diaz del Rio    (ODC Space)
     H.A. Neilan        (JPL)
     W.M. Owen          (JPL)
     W.L. Taber         (JPL)

Version

    SPICELIB Version 1.1.0, 06-JUL-2021 (JDR)

        Added IMPLICIT NONE statement.

        Edited the header to comply with NAIF standard. Added complete
        code example based on existing example.

    SPICELIB Version 1.0.3, 23-APR-2010 (NJB)

        Header correction: assertions that the output
        can overwrite the input have been removed.

    SPICELIB Version 1.0.2, 10-MAR-1992 (WLT)

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

    SPICELIB Version 1.0.1, 09-MAY-1990 (HAN)

        Several errors in the header documentation were corrected.

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