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cggbak.f(3) LAPACK cggbak.f(3)

NAME

cggbak.f -

SYNOPSIS

Functions/Subroutines


subroutine cggbak (JOB, SIDE, N, ILO, IHI, LSCALE, RSCALE, M, V, LDV, INFO)
CGGBAK

Function/Subroutine Documentation

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

CGGBAK

Purpose:


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

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 CGGBAL.

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 CGGBAL.
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 CGGBAL.

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 CGGBAL.

M


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

V


V is COMPLEX array, dimension (LDV,M)
On entry, the matrix of right or left eigenvectors to be
transformed, as returned by CTGEVC.
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 148 of file cggbak.f.

Author

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