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Index Page vnorm_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

       vnorm_c ( Vector norm, 3 dimensions )

       SpiceDouble vnorm_c ( ConstSpiceDouble v1[3] )

#### Abstract

       Compute the magnitude of a double precision 3-dimensional
       vector.

#### Required_Reading

       None.

#### Keywords

       VECTOR

#### Brief_I/O

       VARIABLE  I/O  DESCRIPTION
       --------  ---  --------------------------------------------------
       v1         I   Vector whose magnitude is to be found.

       The function returns the magnitude of `v1'.

#### Detailed_Input

       v1          is any double precision 3-dimensional vector.

#### Detailed_Output

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

#### Parameters

       None.

#### Exceptions

       Error free.

#### Files

       None.

#### Particulars

       vnorm_c takes care to avoid overflow while computing the norm of the
       input vector `v1'. vnorm_c finds the component of `v1' whose magnitude
       is the largest. Calling this magnitude `v1max', the norm is computed
       using the formula:

                            ||    1         ||
          vnorm_c = v1max * || ------- * v1 ||
                            ||  v1max       ||

       where the notation ||x|| indicates the norm of the vector `x'.

#### 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 a set of 3-dimensional vectors and compute the
          magnitude of each vector within.

          Example code begins here.

          /.
             Program vnorm_ex1
          ./
          #include <stdio.h>
          #include "SpiceUsr.h"

          int main( )
          {

             /.
             Local parameters.
             ./
             #define SETSIZ       3

             /.
             Local variables.
             ./
             SpiceInt             i;

             /.
             Define a set of 3-dimensional vectors.
             ./
             SpiceDouble          v1     [SETSIZ][3] = {
                                       { 1.0,    2.0,  2.0   },
                                       { 5.0,   12.0,  0.0   },
                                       {-5.e-17, 0.0, 12.e-17}  };

             /.
             Calculate the magnitude of each vector
             ./
             for ( i = 0; i < SETSIZ; i++ )
             {

                printf( "Input vector:  %9.2e %9.2e %9.2e\n",
                                       v1[i][0], v1[i][1], v1[i][2] );
                printf( "Magnitude   :  %23.20f\n", vnorm_c ( v1[i] ) );
                printf( "\n" );

             }

             return ( 0 );
          }

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

          Input vector:   1.00e+00  2.00e+00  2.00e+00
          Magnitude   :   3.00000000000000000000

          Input vector:   5.00e+00  1.20e+01  0.00e+00
          Magnitude   :  13.00000000000000000000

          Input vector:  -5.00e-17  0.00e+00  1.20e-16
          Magnitude   :   0.00000000000000013000

#### Restrictions

       None.

#### Literature_References

       None.

#### Author_and_Institution

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

#### Version

       -CSPICE Version 1.0.3, 05-JUL-2021 (JDR)

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

       -CSPICE Version 1.0.2, 16-JAN-2008 (EDW)

           Corrected typos in header titles:

           Detailed Input to -Detailed_Input
           Detailed Output to -Detailed_Output

       -CSPICE Version 1.0.1, 12-NOV-2006 (EDW)

           Added -Parameters section header.

       -CSPICE Version 1.0.0, 16-APR-1999 (NJB) (WMO) (WLT)

#### Index_Entries

       norm of 3-dimensional vector

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

    Fri Dec 31 18:41:15 2021