# cggbak.f(3) [centos man page]

```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

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
Generated automatically by Doxygen for LAPACK from the source code.

Version 3.4.2							  Tue Sep 25 2012						       cggbak.f(3)```

## Check Out this Related Man Page

```CGGBAK(l)								 )								 CGGBAK(l)

NAME
CGGBAK  -  form	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

SYNOPSIS
SUBROUTINE CGGBAK( JOB, SIDE, N, ILO, IHI, LSCALE, RSCALE, M, V, LDV, INFO )

CHARACTER	  JOB, SIDE

INTEGER	  IHI, ILO, INFO, LDV, M, N

REAL 	  LSCALE( * ), RSCALE( * )

COMPLEX	  V( LDV, * )

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.

ARGUMENTS
JOB     (input) 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    (input) CHARACTER*1
= 'R':  V contains right eigenvectors;
= 'L':  V contains left eigenvectors.

N       (input) INTEGER
The number of rows of the matrix V.  N >= 0.

ILO     (input) INTEGER
IHI     (input) 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  (input) 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  (input) 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       (input) INTEGER
The number of columns of the matrix V.  M >= 0.

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

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

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

LAPACK version 3.0						   15 June 2000 							 CGGBAK(l)```
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