sggbak.f man page

sggbak.f —

Synopsis

Functions/Subroutines

subroutine sggbak (JOB, SIDE, N, ILO, IHI, LSCALE, RSCALE, M, V, LDV, INFO)
SGGBAK

Function/Subroutine Documentation

subroutine sggbak (characterJOB, characterSIDE, integerN, integerILO, integerIHI, real, dimension( * )LSCALE, real, dimension( * )RSCALE, integerM, real, dimension( ldv, * )V, integerLDV, integerINFO)

SGGBAK

Purpose:

SGGBAK forms the right or left eigenvectors of a real generalized
eigenvalue problem A*x = lambda*B*x, by backward transformation on
the computed eigenvectors of the balanced pair of matrices output by
SGGBAL.

Parameters:

JOB

JOB is CHARACTER*1
Specifies the type of backward transformation required:
= 'N':  do nothing, return immediately;
= 'P':  do backward transformation for permutation only;
= 'S':  do backward transformation for scaling only;
= 'B':  do backward transformations for both permutation and
        scaling.
JOB must be the same as the argument JOB supplied to SGGBAL.

SIDE

SIDE is CHARACTER*1
= 'R':  V contains right eigenvectors;
= 'L':  V contains left eigenvectors.

N

N is INTEGER
The number of rows of the matrix V.  N >= 0.

ILO

ILO is INTEGER

IHI

IHI is INTEGER
The integers ILO and IHI determined by SGGBAL.
1 <= ILO <= IHI <= N, if N > 0; ILO=1 and IHI=0, if N=0.

LSCALE

LSCALE is REAL array, dimension (N)
Details of the permutations and/or scaling factors applied
to the left side of A and B, as returned by SGGBAL.

RSCALE

RSCALE is REAL array, dimension (N)
Details of the permutations and/or scaling factors applied
to the right side of A and B, as returned by SGGBAL.

M

M is INTEGER
The number of columns of the matrix V.  M >= 0.

V

V is REAL array, dimension (LDV,M)
On entry, the matrix of right or left eigenvectors to be
transformed, as returned by STGEVC.
On exit, V is overwritten by the transformed eigenvectors.

LDV

LDV is INTEGER
The leading dimension of the matrix V. LDV >= max(1,N).

INFO

INFO is INTEGER
= 0:  successful exit.
< 0:  if INFO = -i, the i-th argument had an illegal value.

Author:

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Date:

November 2011

Further Details:

See R.C. Ward, Balancing the generalized eigenvalue problem,
               SIAM J. Sci. Stat. Comp. 2 (1981), 141-152.

Definition at line 147 of file sggbak.f.

Author

Generated automatically by Doxygen for LAPACK from the source code.

Referenced By

sggbak(3) is an alias of sggbak.f(3).

Sat Nov 16 2013 Version 3.4.2 LAPACK