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Index Page mxv_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

       mxv_c ( Matrix times vector, 3x3 )

       void mxv_c ( ConstSpiceDouble    m   [3][3],
                    ConstSpiceDouble    vin [3],
                    SpiceDouble         vout[3]    )

#### Abstract

       Multiply a 3x3 double precision matrix with a 3-dimensional
       double precision vector.

#### Required_Reading

       None.

#### Keywords

       MATRIX
       VECTOR

#### Brief_I/O

       VARIABLE  I/O  DESCRIPTION
       --------  ---  --------------------------------------------------
       m          I   3x3 double precision matrix.
       vin        I   3-dimensional double precision vector.
       vout       O   3-dimensional double precision vector. `vout' is
                      the product m*vin.

#### Detailed_Input

       m           is an arbitrary 3x3 double precision matrix.

       vin         is an arbitrary 3-dimensional double precision vector.

#### Detailed_Output

       vout        is a 3-dimensional double precision vector. `vout' is
                   the product m * v. `vout' may overwrite `vin'.

#### Parameters

       None.

#### Exceptions

       Error free.

#### Files

       None.

#### Particulars

       The code reflects precisely the following mathematical expression

          For each value of the subscript `i' from 0 to 2:

                          2
                       .-----
                        \
             vout[i] =   )  m[i][k] * vin[k]
                        /
                       '-----
                         k=0

       The intermediate results of the operation performed by this routine
       are buffered in a temporary vector which is later moved to the output
       vector.  Thus `vout' can be actually be `vin' if desired without
       interfering with the computation.

#### 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) Given a 3x3 matrix and a 3-vector, multiply the matrix by
          the vector.

          Example code begins here.

          /.
             Program mxv_ex1
          ./
          #include <stdio.h>
          #include "SpiceUsr.h"

          int main( )
          {

             /.
             Local variables.
             ./
             SpiceDouble          vout   [3];

             /.
             Define `m' and `vin'.
             ./
             SpiceDouble          m      [3][3] = { { 0.0,  1.0,  0.0},
                                                    {-1.0,  0.0,  0.0},
                                                    { 0.0,  0.0,  1.0} };

             SpiceDouble          vin    [3] = { 1.0,  2.0,  3.0 };

             /.
             Multiply `m' by `vin'.
             ./
             mxv_c ( m, vin, vout );

             printf( "M times VIN:\n" );
             printf( "%10.3f %9.3f %9.3f\n", vout[0], vout[1], vout[2] );

             return ( 0 );
          }

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

          M times VIN:
               2.000    -1.000     3.000

#### Restrictions

       1)  The user is responsible for checking the magnitudes of the
           elements of `m' and `vin' so that a floating point overflow does
           not occur.

#### Literature_References

       None.

#### Author_and_Institution

       J. Diaz del Rio     (ODC Space)
       E.D. Wright         (JPL)

#### Version

       -CSPICE Version 1.1.0, 13-AUG-2021 (JDR)

           Changed input argument name "m1" to "m" for consistency with
           other routines.

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

       -CSPICE Version 1.0.0, 16-APR-1999 (EDW)

#### Index_Entries

       matrix times 3-dimensional vector

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

    Fri Dec 31 18:41:09 2021