Index of Functions: A B C D E F G H I J K L M N O P Q R S T U V W X
Index Page vnormg_c

Table of contents

Procedure Abstract Required_Reading Keywords Brief_I/O Detailed_Input | Detailed_Output Parameters Exceptions Files Particulars Examples | Restrictions Literature_References Author_and_Institution Version Index_Entries

#### Procedure

       vnormg_c ( Vector norm, general dimension )

       SpiceDouble vnormg_c ( ConstSpiceDouble   * v1,
                              SpiceInt             ndim )

#### Abstract

       Compute the magnitude of a double precision vector of arbitrary
       dimension.

#### Required_Reading

       None.

#### Keywords

       VECTOR

#### Brief_I/O

       VARIABLE  I/O  DESCRIPTION
       --------  ---  --------------------------------------------------
       v1         I   Vector whose magnitude is to be found.
       ndim       I   Dimension of `v1'.

       The function returns the magnitude of `v1'.

#### Detailed_Input

       v1          is any double precision vector of arbitrary dimension.

       ndim        is the dimension of the input vector `v1'.

#### Detailed_Output

       The function returns the magnitude of `v1' calculated in a
       numerically stable way.

#### Parameters

       None.

#### Exceptions

       Error free.

#### Files

       None.

#### Particulars

       vnormg_c finds the component of v1 whose magnitude is the largest.
       If the absolute magnitude of that component indicates that a
       numeric overflow would occur when it is squared, or if it
       indicates that an underflow would occur when squared (falsely
       giving a magnitude of zero) then the following expression is
       used:

          vnormg_c = v1max * MAGNITUDE OF [ (1/v1max)*v1 ]

       Otherwise a simpler expression is used:

          vnormg_c = MAGNITUDE OF [ v1 ]

       Beyond the logic described above, no further checking of the
       validity of the input is performed.

#### Examples

       The numerical results shown for these examples 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 a four-dimensional vector and calculate its magnitude.

          Example code begins here.

          /.
             Program vnormg_ex1
          ./
          #include <stdio.h>
          #include "SpiceUsr.h"

          int main( )
          {

             /.
             Local parameters.
             ./
             #define NDIM         4

             /.
             Local variables.
             ./
             SpiceDouble          v1    [NDIM] = { 12.3, -4.32, 76.0, 1.87 };

             /.
             Compute the magnitude of `v1'
             ./
             printf(" Magnitude of v1: %f\n", vnormg_c( v1, NDIM ) );

             return ( 0 );
          }

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

           Magnitude of v1: 77.132673

       2) The following table show the correlation between various input
          vectors `v1' and vnormg_c:

             ndim     v1[ndim]                          vnormg_c
             ---------------------------------------------------
              1      (-7.0e20)                            7.e20
              3      (1., 2., 2.)                         3.
              4      (3., 3., 3., 3.)                     6.
              5      (5., 12., 0., 0., 0.)               13.
              3      (-5.e-17, 0.0, 12.e-17)             13.e-17

#### Restrictions

       None.

#### Literature_References

       None.

#### Author_and_Institution

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

#### Version

       -CSPICE Version 1.2.0, 13-AUG-2021 (JDR)

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

           Removed check for "ndim" being positive in order to replicate
           behavior of SPICELIB equivalent routine.

       -CSPICE Version 1.1.0, 22-OCT-1998 (NJB)

           Made input vector const.

       -CSPICE Version 1.0.0, 01-APR-1998 (EDW) (WMO)

#### Index_Entries

       norm of n-dimensional vector

#### Link to routine vnormg_c source file vnormg_c.c

    Fri Dec 31 18:41:15 2021