Example 2 (from Program LA_GEES

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Example 2 (from Program LA_GEES_EXAMPLE)

Matrix

as in Example 1.

Function SELECT is:


 		 LOGICAL FUNCTION SELECT(X,Y) 


USE LA_PRECISION, ONLY: WP  wp 


INTRINSIC EPSILON 


REAL(WP), INTENT(IN) :: X,Y 

! 		 		 Select the real eigenvalues 

! 		 		 within the working precision 


IF (ABS(Y)  EPSILON(1.0_WP)) THEN 


SELECT = .TRUE. 


ELSE 


SELECT = .FALSE. 


END IF 


END FUNCTION SELECT

The call:
CALL LA_GEES( A, WR, WI, VS, SELECT, SDIM, INFO )

${\bf A}$ , ${\bf WR}$ , ${\bf WI}$ , ${\bf VS}$ , ${\bf SDIM}$ , and ${\bf INFO}$ on exit:

$\begin{displaymath} \begin{array}{c} {\bf A} \\ \begin{array}{\vert lllll\ver... ...mes 10^{1} & \;\;\:4.45961 \\ \hline \end{array} \end{array} \end{displaymath}$

$\begin{displaymath} \begin{array}{c} {\bf WR} \\ \begin{array}{\vert r\vert} ... ...61 \\ 3.80078 \\ -3.80078 \\ \hline \end{array} \end{array} \end{displaymath}$

$\begin{displaymath} \begin{array}{c} {\bf VS} \\ \par\begin{array}{\vert r@{\hs... ...} & -3.02161 \times 10^{-1} \\ \hline \end{array} \end{array}\end{displaymath}$

$\begin{displaymath} {\bf SDIM} = 1, \hspace{5mm} {\bf INFO} = 0 \end{displaymath}$

The real-Schur form

, the matrix of Schur vectors

, and the eigenvalues of matrix

are:

$\begin{displaymath} T = \left( \begin{array}{rlrlr} -5.48541 & -1.53935 & -1.02... ...00000 & ~~1.00533 \times 10^{1} & 4.45961 \end{array} \right), \end{displaymath}$

$\begin{displaymath} Z = \left( \begin{array}{@{\hspace{1mm}}r@{\hspace{1mm}}r@{... ... \times 10^{-1} & -3.02161 \times 10^{-1} \end{array} \right), \end{displaymath}$

and

$\begin{displaymath} \left( \begin{array}{l} -5.48541 \\ -2.21691 + 8.59661i \... ... 3.80078i \\ \;\;\; 4.45961 - 3.80078i \end{array} \right). \end{displaymath}$

Next: LA_GEESX Up: Examples Previous: Example 1 (from Program Contents Index

Susan Blackford 2001-08-19