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Index Page mxm_c

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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

       mxm_c ( Matrix times matrix, 3x3 )

       void mxm_c ( ConstSpiceDouble   m1  [3][3],
                    ConstSpiceDouble   m2  [3][3],
                    SpiceDouble        mout[3][3] )

#### Abstract

       Multiply two 3x3 matrices.

#### Required_Reading

       None.

#### Keywords

       MATRIX

#### Brief_I/O

       VARIABLE  I/O  DESCRIPTION
       --------  ---  --------------------------------------------------
       m1         I   3x3 double precision matrix.
       m2         I   3x3 double precision matrix.
       mout       O   The 3x3 double precision matrix product m1*m2.

#### Detailed_Input

       m1          is an arbitrary 3x3 double precision matrix.

       m2          is an arbitrary 3x3 double precision matrix.

#### Detailed_Output

       mout        is a 3x3 double precision matrix. `mout' is the product
                   m1*m2.

#### Parameters

       None.

#### Exceptions

       Error free.

#### Files

       None.

#### Particulars

       The code reflects precisely the following mathematical expression

          For each value of the subscripts `i' and `j' from 0 to 2:

                             2
                          .-----
                           \
             mout[i][j] =   )  m1[i][k] * m2[k][j]
                           /
                          '-----
                            k=0

       The intermediate results of the operation above are buffered in a
       temporary matrix which is later moved to the output matrix.
       Thus, to save space in the calling program, `mout' can be actually
       be `m1' or `m2' if desired without interfering with the computations.

#### 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 two 3x3 double precision matrices, compute their
          product.

          Example code begins here.

          /.
             Program mxm_ex1
          ./
          #include <stdio.h>
          #include "SpiceUsr.h"

          int main( )
          {

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

             SpiceInt             i;

             /.
             Define `m1' and `m2'.
             ./
             SpiceDouble          m1     [3][3] = { { 1.0,  1.0,  0.0},
                                                    {-1.0,  1.0,  0.0},
                                                    { 0.0,  0.0,  1.0} };

             SpiceDouble          m2     [3][3] = { { 1.0,  0.0,  0.0},
                                                    { 0.0,  1.0,  1.0},
                                                    { 0.0, -1.0,  1.0} };

             /.
             Compute `m1' times `m2'.
             ./
             mxm_c ( m1, m2, mout );

             printf( "M1:\n" );
             for ( i = 0; i < 3; i++ )
             {
                printf( "%16.7f %15.7f %15.7f\n", m1[i][0], m1[i][1], m1[i][2] );
             }

             printf( "\n" );
             printf( "M2:\n" );
             for ( i = 0; i < 3; i++ )
             {
                printf( "%16.7f %15.7f %15.7f\n", m2[i][0], m2[i][1], m2[i][2] );
             }

             printf( "\n" );
             printf( "M1 times M2:\n" );
             for ( i = 0; i < 3; i++ )
             {
                printf( "%16.7f %15.7f %15.7f\n",
                        mout[i][0], mout[i][1], mout[i][2] );
             }

             return ( 0 );
          }

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

          M1:
                 1.0000000       1.0000000       0.0000000
                -1.0000000       1.0000000       0.0000000
                 0.0000000       0.0000000       1.0000000

          M2:
                 1.0000000       0.0000000       0.0000000
                 0.0000000       1.0000000       1.0000000
                 0.0000000      -1.0000000       1.0000000

          M1 times M2:
                 1.0000000       1.0000000       1.0000000
                -1.0000000       1.0000000       1.0000000
                 0.0000000      -1.0000000       1.0000000

#### Restrictions

       None.

#### Literature_References

       None.

#### Author_and_Institution

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

#### Version

       -CSPICE Version 1.0.1, 05-JUN-2020 (JDR)

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

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

#### Index_Entries

       matrix times matrix 3x3_case

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

    Fri Dec 31 18:41:09 2021