Index Page mxmt_c

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

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

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

#### Abstract

        Multiply a 3x3 matrix and the transpose of another 3x3 matrix.

#### 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 product m1 times m2 transpose .

#### Detailed_Input

       m1         is an arbitrary 3x3 double precision matrix.

       m2         is an arbitrary 3x3 double precision matrix.
                  Typically, m2 will be a rotation matrix since
                  then its transpose is its inverse (but this is
                  NOT a requirement).

#### Detailed_Output

       mout       is a 3x3 double precision matrix. mout is the
                  product

                                  t
                     mout = m1  m2

                  mout may overwrite either m1 or 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[j][k]
                        k=0

       Note that the reversal of the k and i subscripts in the left-hand
       matrix m1 is what makes mout the product of the TRANSPOSE of M1
       and not simply of m1 itself.  Also, the intermediate results of
       the operation above are buffered in a temporary matrix which is
       later moved to the output matrix.  Thus mout can be actually be
       m1 or m2 if desired without interfering with the computations.

#### Examples

       Let  m1 = |  0.0  1.0  0.0 |
                 |                |
                 | -1.0  0.0  0.0 |
                 |                |
                 |  0.0  0.0  1.0 |

            m2 = |  0.0  1.0  0.0 |
                 |                |
                 | -1.0  0.0  0.0 |
                 |                |
                 |  0.0  0.0  1.0 |

       then the call

       mxmt_c ( m1, m2, mout );

       produces the matrix

       mout = | 1.0  0.0  0.0 |
              |               |
              | 0.0  1.0  0.0 |
              |               |
              | 0.0  0.0  1.0 |

#### Restrictions

       The user is responsible for checking the magnitudes of the
       elements of m1 and m2 so that a floating point overflow does
       not occur.  (In the typical use where m1 and m2 are rotation
       matrices, this not a risk at all.)

#### Literature_References

       None.

#### Author_and_Institution

       W.M. Owen       (JPL)
       E.D. Wright     (JPL)

#### Version

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

#### Index_Entries

       matrix times matrix_transpose 3x3_case

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

    Wed Apr  5 17:54:39 2017