Home Man
Search
Today's Posts
Register

Linux & Unix Commands - Search Man Pages

RedHat 9 (Linux i386) - man page for dtgex2 (redhat section l)

DTGEX2(l)					)					DTGEX2(l)

NAME
       DTGEX2  - swap adjacent diagonal blocks (A11, B11) and (A22, B22) of size 1-by-1 or 2-by-2
       in an upper (quasi) triangular matrix pair (A, B) by an orthogonal equivalence transforma-
       tion

SYNOPSIS
       SUBROUTINE DTGEX2( WANTQ,  WANTZ,  N,  A,  LDA,	B, LDB, Q, LDQ, Z, LDZ, J1, N1, N2, WORK,
			  LWORK, INFO )

	   LOGICAL	  WANTQ, WANTZ

	   INTEGER	  INFO, J1, LDA, LDB, LDQ, LDZ, LWORK, N, N1, N2

	   DOUBLE	  PRECISION A( LDA, * ), B( LDB, * ), Q( LDQ, * ), WORK( * ), Z( LDZ, * )

PURPOSE
       DTGEX2 swaps adjacent diagonal blocks (A11, B11) and (A22, B22) of size 1-by-1  or  2-by-2
       in an upper (quasi) triangular matrix pair (A, B) by an orthogonal equivalence transforma-
       tion.  (A, B) must be in generalized real Schur canonical form  (as  returned  by  DGGES),
       i.e. A is block upper triangular with 1-by-1 and 2-by-2 diagonal blocks. B is upper trian-
       gular.

       Optionally, the matrices Q and Z of generalized Schur vectors are updated.

	      Q(in) * A(in) * Z(in)' = Q(out) * A(out) * Z(out)'
	      Q(in) * B(in) * Z(in)' = Q(out) * B(out) * Z(out)'

ARGUMENTS
       WANTQ   (input) LOGICAL

       WANTZ   (input) LOGICAL

       N       (input) INTEGER
	       The order of the matrices A and B. N >= 0.

       A      (input/output) DOUBLE PRECISION arrays, dimensions (LDA,N)
	      On entry, the matrix A in the pair (A, B).  On exit, the updated matrix A.

       LDA     (input)	INTEGER
	       The leading dimension of the array A. LDA >= max(1,N).

       B      (input/output) DOUBLE PRECISION arrays, dimensions (LDB,N)
	      On entry, the matrix B in the pair (A, B).  On exit, the updated matrix B.

       LDB     (input)	INTEGER
	       The leading dimension of the array B. LDB >= max(1,N).

       Q       (input/output) DOUBLE PRECISION array, dimension (LDZ,N)
	       On entry, if WANTQ = .TRUE., the orthogonal matrix Q.  On exit, the updated matrix
	       Q.  Not referenced if WANTQ = .FALSE..

       LDQ     (input) INTEGER
	       The leading dimension of the array Q. LDQ >= 1.	If WANTQ = .TRUE., LDQ >= N.

       Z       (input/output) DOUBLE PRECISION array, dimension (LDZ,N)
	       On  entry, if WANTZ =.TRUE., the orthogonal matrix Z.  On exit, the updated matrix
	       Z.  Not referenced if WANTZ = .FALSE..

       LDZ     (input) INTEGER
	       The leading dimension of the array Z. LDZ >= 1.	If WANTZ = .TRUE., LDZ >= N.

       J1      (input) INTEGER
	       The index to the first block (A11, B11). 1 <= J1 <= N.

       N1      (input) INTEGER
	       The order of the first block (A11, B11). N1 = 0, 1 or 2.

       N2      (input) INTEGER
	       The order of the second block (A22, B22). N2 = 0, 1 or 2.

       WORK    (workspace) DOUBLE PRECISION array, dimension (LWORK).

       LWORK   (input) INTEGER
	       The dimension of the array WORK.  LWORK >=  MAX( N*(N2+N1), (N2+N1)*(N2+N1)*2 )

       INFO    (output) INTEGER
	       =0: Successful exit
	       >0: If INFO = 1, the transformed matrix (A, B) would be too far	from  generalized
	       Schur  form;  the blocks are not swapped and (A, B) and (Q, Z) are unchanged.  The
	       problem of swapping is too ill-conditioned.  <0: If  INFO  =  -16:  LWORK  is  too
	       small. Appropriate value for LWORK is returned in WORK(1).

FURTHER DETAILS
       Based on contributions by
	  Bo Kagstrom and Peter Poromaa, Department of Computing Science,
	  Umea University, S-901 87 Umea, Sweden.

       In  the current code both weak and strong stability tests are performed. The user can omit
       the strong stability test by changing the internal logical parameter WANDS to .FALSE.. See
       ref. [2] for details.

       [1] B. Kagstrom; A Direct Method for Reordering Eigenvalues in the
	   Generalized Real Schur Form of a Regular Matrix Pair (A, B), in
	   M.S. Moonen et al (eds), Linear Algebra for Large Scale and
	   Real-Time Applications, Kluwer Academic Publ. 1993, pp 195-218.

       [2] B. Kagstrom and P. Poromaa; Computing Eigenspaces with Specified
	   Eigenvalues of a Regular Matrix Pair (A, B) and Condition
	   Estimation: Theory, Algorithms and Software,
	   Report UMINF - 94.04, Department of Computing Science, Umea
	   University, S-901 87 Umea, Sweden, 1994. Also as LAPACK Working
	   Note 87. To appear in Numerical Algorithms, 1996.

LAPACK version 3.0			   15 June 2000 				DTGEX2(l)


All times are GMT -4. The time now is 09:36 AM.

Unix & Linux Forums Content Copyrightę1993-2018. All Rights Reserved.
UNIX.COM Login
Username:
Password:  
Show Password