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Index Page vdot_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

       vdot_c ( Vector dot product, 3 dimensions )

       SpiceDouble vdot_c ( ConstSpiceDouble   v1[3],
                            ConstSpiceDouble   v2[3] )

#### Abstract

       Compute the dot product of two double precision, 3-dimensional
       vectors.

#### Required_Reading

       None.

#### Keywords

       VECTOR

#### Brief_I/O

       VARIABLE  I/O  DESCRIPTION
       --------  ---  --------------------------------------------------
       v1         I   First vector in the dot product.
       v2         I   Second vector in the dot product.

       The function returns the value of the dot product of `v1' and `v2'.

#### Detailed_Input

       v1,
       v2          are two arbitrary double precision 3-dimensional
                   vectors.

#### Detailed_Output

       The function returns the value of the dot product (inner product)
       of `v1' and `v2':

          < v1, v2 >

#### Parameters

       None.

#### Exceptions

       Error free.

#### Files

       None.

#### Particulars

       vdot_c calculates the dot product of `v1' and `v2' by a simple
       application of the definition:

                       1
                    .-----
                     \
          vdot_c  =   )  v1[i] * v2[i]
                     /
                    '-----
                      i=0

       No error checking is performed to prevent or recover from numeric
       overflow.

#### 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) Suppose that you have a set of double precision 3-dimensional
          vectors. Check if they are orthogonal to the Z-axis.

          Example code begins here.

          /.
             Program vdot_ex1
          ./
          #include <stdio.h>
          #include "SpiceUsr.h"

          int main( )
          {

             /.
             Local parameters.
             ./
             #define SETSIZ       4

             /.
             Local variables.
             ./
             SpiceInt             i;

             /.
             Define the vector set.
             ./
             SpiceDouble          v1     [SETSIZ][3] = {
                                                  { 1.0,  0.0,  0.0 },
                                                  { 0.0, -6.0,  0.0 },
                                                  {10.0,  0.0, -1.0 },
                                                  { 0.0,  0.0,  1.0 } };

             SpiceDouble          z      [3]    = { 0.0,  0.0,  1.0 };

             /.
             Check the orthogonality with respect to `z' of each
             vector in `v1'.
             ./
             for ( i = 0; i < SETSIZ; i++ )
             {

                printf( "\n" );
                printf( "Input vector (V1):  %5.1f %5.1f %5.1f\n",
                                  v1[i][0], v1[i][1], v1[i][2] );

                if ( vdot_c ( v1[i], z ) == 0.0 )
                {
                   printf( "V1 and Z are orthogonal.\n" );
                }
                else
                {
                   printf( "V1 and Z are NOT orthogonal.\n" );
                }

             }

             return ( 0 );
          }

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

          Input vector (V1):    1.0   0.0   0.0
          V1 and Z are orthogonal.

          Input vector (V1):    0.0  -6.0   0.0
          V1 and Z are orthogonal.

          Input vector (V1):   10.0   0.0  -1.0
          V1 and Z are NOT orthogonal.

          Input vector (V1):    0.0   0.0   1.0
          V1 and Z are NOT orthogonal.

#### Restrictions

       1)  The user is responsible for determining that the vectors `v1'
           and `v2' are not so large as to cause numeric overflow. In
           most cases this will not present a problem.

#### 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 1.0.3, 10-AUG-2021 (JDR)

           Edited the header to comply with NAIF standard. Added complete
           code example. Improved -Particulars section.

       -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 (EDW) (WMO) (NJB)

#### Index_Entries

       dot product 3-dimensional vectors

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

    Fri Dec 31 18:41:14 2021