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strexc(3) [debian man page]

strexc.f(3)							      LAPACK							       strexc.f(3)

NAME

       strexc.f -

SYNOPSIS

   Functions/Subroutines
       subroutine strexc (COMPQ, N, T, LDT, Q, LDQ, IFST, ILST, WORK, INFO)
	   STREXC

Function/Subroutine Documentation
   subroutine strexc (characterCOMPQ, integerN, real, dimension( ldt, * )T, integerLDT, real, dimension( ldq, * )Q, integerLDQ, integerIFST,
       integerILST, real, dimension( * )WORK, integerINFO)
       STREXC

       Purpose:

	    STREXC reorders the real Schur factorization of a real matrix
	    A = Q*T*Q**T, so that the diagonal block of T with row index IFST is
	    moved to row ILST.

	    The real Schur form T is reordered by an orthogonal similarity
	    transformation Z**T*T*Z, and optionally the matrix Q of Schur vectors
	    is updated by postmultiplying it with Z.

	    T must be in Schur canonical form (as returned by SHSEQR), that is,
	    block upper triangular with 1-by-1 and 2-by-2 diagonal blocks; each
	    2-by-2 diagonal block has its diagonal elements equal and its
	    off-diagonal elements of opposite sign.

       Parameters:
	   COMPQ

		     COMPQ is CHARACTER*1
		     = 'V':  update the matrix Q of Schur vectors;
		     = 'N':  do not update Q.

	   N

		     N is INTEGER
		     The order of the matrix T. N >= 0.

	   T

		     T is REAL array, dimension (LDT,N)
		     On entry, the upper quasi-triangular matrix T, in Schur
		     Schur canonical form.
		     On exit, the reordered upper quasi-triangular matrix, again
		     in Schur canonical form.

	   LDT

		     LDT is INTEGER
		     The leading dimension of the array T. LDT >= max(1,N).

	   Q

		     Q is REAL array, dimension (LDQ,N)
		     On entry, if COMPQ = 'V', the matrix Q of Schur vectors.
		     On exit, if COMPQ = 'V', Q has been postmultiplied by the
		     orthogonal transformation matrix Z which reorders T.
		     If COMPQ = 'N', Q is not referenced.

	   LDQ

		     LDQ is INTEGER
		     The leading dimension of the array Q.  LDQ >= max(1,N).

	   IFST

		     IFST is INTEGER

	   ILST

		     ILST is INTEGER

		     Specify the reordering of the diagonal blocks of T.
		     The block with row index IFST is moved to row ILST, by a
		     sequence of transpositions between adjacent blocks.
		     On exit, if IFST pointed on entry to the second row of a
		     2-by-2 block, it is changed to point to the first row; ILST
		     always points to the first row of the block in its final
		     position (which may differ from its input value by +1 or -1).
		     1 <= IFST <= N; 1 <= ILST <= N.

	   WORK

		     WORK is REAL array, dimension (N)

	   INFO

		     INFO is INTEGER
		     = 0:  successful exit
		     < 0:  if INFO = -i, the i-th argument had an illegal value
		     = 1:  two adjacent blocks were too close to swap (the problem
			   is very ill-conditioned); T may have been partially
			   reordered, and ILST points to the first row of the
			   current position of the block being moved.

       Author:
	   Univ. of Tennessee

	   Univ. of California Berkeley

	   Univ. of Colorado Denver

	   NAG Ltd.

       Date:
	   November 2011

       Definition at line 146 of file strexc.f.

Author
       Generated automatically by Doxygen for LAPACK from the source code.

Version 3.4.1							  Sun May 26 2013						       strexc.f(3)

Check Out this Related Man Page

DTREXC(l)								 )								 DTREXC(l)

NAME

       DTREXC  -  reorder the real Schur factorization of a real matrix A = Q*T*Q**T, so that the diagonal block of T with row index IFST is moved
       to row ILST

SYNOPSIS

       SUBROUTINE DTREXC( COMPQ, N, T, LDT, Q, LDQ, IFST, ILST, WORK, INFO )

	   CHARACTER	  COMPQ

	   INTEGER	  IFST, ILST, INFO, LDQ, LDT, N

	   DOUBLE	  PRECISION Q( LDQ, * ), T( LDT, * ), WORK( * )

PURPOSE

       DTREXC reorders the real Schur factorization of a real matrix A = Q*T*Q**T, so that the diagonal block of T with row index IFST is moved to
       row  ILST.   The  real  Schur form T is reordered by an orthogonal similarity transformation Z**T*T*Z, and optionally the matrix Q of Schur
       vectors is updated by postmultiplying it with Z.

       T must be in Schur canonical form (as returned by DHSEQR), that is, block upper triangular with 1-by-1 and  2-by-2  diagonal  blocks;  each
       2-by-2 diagonal block has its diagonal elements equal and its off-diagonal elements of opposite sign.

ARGUMENTS

       COMPQ   (input) CHARACTER*1
	       = 'V':  update the matrix Q of Schur vectors;
	       = 'N':  do not update Q.

       N       (input) INTEGER
	       The order of the matrix T. N >= 0.

       T       (input/output) DOUBLE PRECISION array, dimension (LDT,N)
	       On  entry,  the	upper  quasi-triangular  matrix  T,  in Schur Schur canonical form.  On exit, the reordered upper quasi-triangular
	       matrix, again in Schur canonical form.

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

       Q       (input/output) DOUBLE PRECISION array, dimension (LDQ,N)
	       On entry, if COMPQ = 'V', the matrix Q of Schur vectors.  On exit, if COMPQ = 'V', Q has  been  postmultiplied  by  the	orthogonal
	       transformation matrix Z which reorders T.  If COMPQ = 'N', Q is not referenced.

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

       IFST    (input/output) INTEGER
	       ILST	(input/output)	INTEGER Specify the reordering of the diagonal blocks of T.  The block with row index IFST is moved to row
	       ILST, by a sequence of transpositions between adjacent blocks.  On exit, if IFST pointed on entry to the second	row  of  a  2-by-2
	       block,  it  is changed to point to the first row; ILST always points to the first row of the block in its final position (which may
	       differ from its input value by +1 or -1).  1 <= IFST <= N; 1 <= ILST <= N.

       WORK    (workspace) DOUBLE PRECISION array, dimension (N)

       INFO    (output) INTEGER
	       = 0:  successful exit
	       < 0:  if INFO = -i, the i-th argument had an illegal value
	       = 1:  two adjacent blocks were too close to swap (the problem is very ill-conditioned); T may have been	partially  reordered,  and
	       ILST points to the first row of the current position of the block being moved.

LAPACK version 3.0						   15 June 2000 							 DTREXC(l)
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