cggbak.f - Man Page
SRC/cggbak.f
Synopsis
Functions/Subroutines
subroutine cggbak (job, side, n, ilo, ihi, lscale, rscale, m, v, ldv, info)
CGGBAK
Function/Subroutine Documentation
subroutine cggbak (character job, character side, integer n, integer ilo, integer ihi, real, dimension( * ) lscale, real, dimension( * ) rscale, integer m, complex, dimension( ldv, * ) v, integer ldv, integer info)
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.
Further Details:
See R.C. Ward, Balancing the generalized eigenvalue problem, SIAM J. Sci. Stat. Comp. 2 (1981), 141-152.
Definition at line 146 of file cggbak.f.
Author
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Referenced By
The man page cggbak(3) is an alias of cggbak.f(3).
Tue Nov 28 2023 12:08:41 Version 3.12.0 LAPACK