dlaexc(l) [redhat man page]

DLAEXC(l)								 )								 DLAEXC(l)

NAME

       DLAEXC - swap adjacent diagonal blocks T11 and T22 of order 1 or 2 in an upper quasi-triangular matrix T by an orthogonal similarity trans-
       formation

SYNOPSIS

       SUBROUTINE DLAEXC( WANTQ, N, T, LDT, Q, LDQ, J1, N1, N2, WORK, INFO )

	   LOGICAL	  WANTQ

	   INTEGER	  INFO, J1, LDQ, LDT, N, N1, N2

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

PURPOSE

       DLAEXC swaps adjacent diagonal blocks T11 and T22 of order 1 or 2 in an upper quasi-triangular matrix T by an orthogonal similarity  trans-
       formation.  T must be in Schur canonical form, that is, block upper triangular with 1-by-1 and 2-by-2 diagonal blocks; each 2-by-2 diagonal
       block has its diagonal elemnts equal and its off-diagonal elements of opposite sign.

ARGUMENTS

       WANTQ   (input) LOGICAL
	       = .TRUE. : accumulate the transformation in the matrix Q;
	       = .FALSE.: do not accumulate the transformation.

       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 canonical form.	On exit, the updated matrix T, 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 WANTQ is .TRUE., the orthogonal matrix Q.	On exit, if WANTQ is .TRUE., the updated matrix Q.  If WANTQ is .FALSE., Q
	       is not referenced.

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

       J1      (input) INTEGER
	       The index of the first row of the first block T11.

       N1      (input) INTEGER
	       The order of the first block T11. N1 = 0, 1 or 2.

       N2      (input) INTEGER
	       The order of the second block T22. N2 = 0, 1 or 2.

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

       INFO    (output) INTEGER
	       = 0: successful exit
	       = 1: the transformed matrix T would be too far from Schur form; the blocks are not swapped and T and Q are unchanged.

LAPACK version 3.0						   15 June 2000 							 DLAEXC(l)

slaexc.f(3)							      LAPACK							       slaexc.f(3)

NAME

       slaexc.f -

SYNOPSIS

   Functions/Subroutines
       subroutine slaexc (WANTQ, N, T, LDT, Q, LDQ, J1, N1, N2, WORK, INFO)
	   SLAEXC

Function/Subroutine Documentation
   subroutine slaexc (logicalWANTQ, integerN, real, dimension( ldt, * )T, integerLDT, real, dimension( ldq, * )Q, integerLDQ, integerJ1,
       integerN1, integerN2, real, dimension( * )WORK, integerINFO)
       SLAEXC

       Purpose:

	    SLAEXC swaps adjacent diagonal blocks T11 and T22 of order 1 or 2 in
	    an upper quasi-triangular matrix T by an orthogonal similarity
	    transformation.

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

       Parameters:
	   WANTQ

		     WANTQ is LOGICAL
		     = .TRUE. : accumulate the transformation in the matrix Q;
		     = .FALSE.: do not accumulate the transformation.

	   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
		     canonical form.
		     On exit, the updated matrix T, 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 WANTQ is .TRUE., the orthogonal matrix Q.
		     On exit, if WANTQ is .TRUE., the updated matrix Q.
		     If WANTQ is .FALSE., Q is not referenced.

	   LDQ

		     LDQ is INTEGER
		     The leading dimension of the array Q.
		     LDQ >= 1; and if WANTQ is .TRUE., LDQ >= N.

	   J1

		     J1 is INTEGER
		     The index of the first row of the first block T11.

	   N1

		     N1 is INTEGER
		     The order of the first block T11. N1 = 0, 1 or 2.

	   N2

		     N2 is INTEGER
		     The order of the second block T22. N2 = 0, 1 or 2.

	   WORK

		     WORK is REAL array, dimension (N)

	   INFO

		     INFO is INTEGER
		     = 0: successful exit
		     = 1: the transformed matrix T would be too far from Schur
			  form; the blocks are not swapped and T and Q are
			  unchanged.

       Author:
	   Univ. of Tennessee

	   Univ. of California Berkeley

	   Univ. of Colorado Denver

	   NAG Ltd.

       Date:
	   November 2011

       Definition at line 138 of file slaexc.f.

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

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