Contents
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
SUBROUTINE CGGBAK(JOB, SIDE, N, ILO, IHI, LSCALE, RSCALE, M, V, LDV,
INFO)
CHARACTER * 1 JOB, SIDE
COMPLEX V(LDV,*)
INTEGER N, ILO, IHI, M, LDV, INFO
REAL LSCALE(*), RSCALE(*)
SUBROUTINE CGGBAK_64(JOB, SIDE, N, ILO, IHI, LSCALE, RSCALE, M, V,
LDV, INFO)
CHARACTER * 1 JOB, SIDE
COMPLEX V(LDV,*)
INTEGER*8 N, ILO, IHI, M, LDV, INFO
REAL LSCALE(*), RSCALE(*)
F95 INTERFACE
SUBROUTINE GGBAK(JOB, SIDE, [N], ILO, IHI, LSCALE, RSCALE, [M], V,
[LDV], [INFO])
CHARACTER(LEN=1) :: JOB, SIDE
COMPLEX, DIMENSION(:,:) :: V
INTEGER :: N, ILO, IHI, M, LDV, INFO
REAL, DIMENSION(:) :: LSCALE, RSCALE
SUBROUTINE GGBAK_64(JOB, SIDE, [N], ILO, IHI, LSCALE, RSCALE, [M], V,
[LDV], [INFO])
CHARACTER(LEN=1) :: JOB, SIDE
COMPLEX, DIMENSION(:,:) :: V
INTEGER(8) :: N, ILO, IHI, M, LDV, INFO
REAL, DIMENSION(:) :: LSCALE, RSCALE
C INTERFACE
#include <sunperf.h>
void cggbak(char job, char side, int n, int ilo, int ihi,
float *lscale, float *rscale, int m, complex *v,
int ldv, int *info);
void cggbak_64(char job, char side, long n, long ilo, long
ihi, float *lscale, float *rscale, long m, complex
*v, long ldv, long *info);
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.
JOB (input)
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 per-
mutation and scaling. JOB must be the same as the
argument JOB supplied to CGGBAL.
SIDE (input)
= 'R': V contains right eigenvectors;
= 'L': V contains left eigenvectors.
N (input) The number of rows of the matrix V. N >= 0.
ILO (input)
The integers ILO and IHI determined by CGGBAL. 1
<= ILO <= IHI <= N, if N > 0; ILO=1 and IHI=0, if
N=0.
IHI (input)
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)
Details of the permutations and/or scaling factors
applied to the left side of A and B, as returned
by CGGBAL.
RSCALE (input)
Details of the permutations and/or scaling factors
applied to the right side of A and B, as returned
by CGGBAL.
M (input) The number of columns of the matrix V. M >= 0.
V (input/output)
On entry, the matrix of right or left eigenvectors
to be transformed, as returned by CTGEVC. On
exit, V is overwritten by the transformed eigen-
vectors.
LDV (input)
The leading dimension of the matrix V. LDV >=
max(1,N).
INFO (output)
= 0: successful exit.
< 0: if INFO = -i, the i-th argument had an ille-
gal value.
See R.C. Ward, Balancing the generalized eigenvalue problem,
SIAM J. Sci. Stat. Comp. 2 (1981), 141-152.