\brief \b ESMF_DLAEXC swaps adjacent diagonal blocks of a real upper quasi-triangular matrix in Schur canonical form, by an orthogonal similarity transformation. \htmlonly Download ESMF_DLAEXC + dependencies [TGZ] [ZIP] [TXT] \endhtmlonly \par Purpose:
\verbatim
ESMF_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. \endverbatim \param[in] WANTQ \verbatim WANTQ is LOGICAL = .TRUE. : accumulate the transformation in the matrix Q; = .FALSE.: do not accumulate the transformation. \endverbatim
\param[in] N \verbatim N is INTEGER The order of the matrix T. N >= 0. \endverbatim
\param[in,out] T \verbatim 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. \endverbatim
\param[in] LDT \verbatim LDT is INTEGER The leading dimension of the array T. LDT >= max(1,N). \endverbatim
\param[in,out] Q \verbatim 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. \endverbatim
\param[in] LDQ \verbatim LDQ is INTEGER The leading dimension of the array Q. LDQ >= 1; and if WANTQ is .TRUE., LDQ >= N. \endverbatim
\param[in] J1 \verbatim J1 is INTEGER The index of the first row of the first block T11. \endverbatim
\param[in] N1 \verbatim N1 is INTEGER The order of the first block T11. N1 = 0, 1 or 2. \endverbatim
\param[in] N2 \verbatim N2 is INTEGER The order of the second block T22. N2 = 0, 1 or 2. \endverbatim
\param[out] WORK \verbatim WORK is DOUBLE PRECISION array, dimension (N) \endverbatim
\param[out] INFO \verbatim 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. \endverbatim \author Univ. of Tennessee \author Univ. of California Berkeley \author Univ. of Colorado Denver \author NAG Ltd. \date December 2016 \ingroup doubleOTHERauxiliary
| Type | Intent | Optional | Attributes | Name | ||
|---|---|---|---|---|---|---|
| logical | :: | WANTQ | ||||
| integer | :: | N | ||||
| double precision | :: | T(LDT,*) | ||||
| integer | :: | LDT | ||||
| double precision | :: | Q(LDQ,*) | ||||
| integer | :: | LDQ | ||||
| integer | :: | J1 | ||||
| integer | :: | N1 | ||||
| integer | :: | N2 | ||||
| double precision | :: | WORK(*) | ||||
| integer | :: | INFO |