Provided by: liblapack-doc_3.3.1-1_all bug

NAME

       LAPACK-3  -  swaps adjacent diagonal blocks T11 and T22 of order 1 or 2 in an upper quasi-
       triangular matrix T by an orthogonal similarity transformation

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 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.

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 auxiliary routine (version 3.2.2)   April 2011                            DLAEXC(3lapack)