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dlaexc.f(3) [centos man page]

dlaexc.f(3)							      LAPACK							       dlaexc.f(3)

NAME

       dlaexc.f -

SYNOPSIS

   Functions/Subroutines
       subroutine dlaexc (WANTQ, N, T, LDT, Q, LDQ, J1, N1, N2, WORK, INFO)
	   DLAEXC swaps adjacent diagonal blocks of a real upper quasi-triangular matrix in Schur canonical form, by an orthogonal similarity
	   transformation.

Function/Subroutine Documentation
   subroutine dlaexc (logicalWANTQ, integerN, double precision, dimension( ldt, * )T, integerLDT, double precision, dimension( ldq, * )Q,
       integerLDQ, integerJ1, integerN1, integerN2, double precision, dimension( * )WORK, integerINFO)
       DLAEXC swaps adjacent diagonal blocks of a real upper quasi-triangular matrix in Schur canonical form, by an orthogonal similarity
       transformation.

       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
	    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 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

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

	   Q

		     Q is 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

		     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 DOUBLE PRECISION 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:
	   September 2012

       Definition at line 138 of file dlaexc.f.

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

Version 3.4.2							  Tue Sep 25 2012						       dlaexc.f(3)

Check Out this Related Man Page

SLAEXC(l)								 )								 SLAEXC(l)

NAME

       SLAEXC - 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 SLAEXC( WANTQ, N, T, LDT, Q, LDQ, J1, N1, N2, WORK, INFO )

	   LOGICAL	  WANTQ

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

	   REAL 	  Q( LDQ, * ), T( LDT, * ), WORK( * )

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

       Q       (input/output) 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     (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) REAL 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 							 SLAEXC(l)
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