SGEBAK(l) ) SGEBAK(l)
SGEBAK - form the right or left eigenvectors of a real general matrix by backward trans-
formation on the computed eigenvectors of the balanced matrix output by SGEBAL
SUBROUTINE SGEBAK( JOB, SIDE, N, ILO, IHI, SCALE, M, V, LDV, INFO )
CHARACTER JOB, SIDE
INTEGER IHI, ILO, INFO, LDV, M, N
REAL V( LDV, * ), SCALE( * )
SGEBAK forms the right or left eigenvectors of a real general matrix by backward transfor-
mation on the computed eigenvectors of the balanced matrix output by SGEBAL.
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
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 SGEBAL. 1 <= ILO
<= IHI <= N, if N > 0; ILO=1 and IHI=0, if N=0.
SCALE (input) REAL array, dimension (N)
Details of the permutation and scaling factors, as returned by SGEBAL.
M (input) INTEGER
The number of columns of the matrix V. M >= 0.
V (input/output) REAL array, dimension (LDV,M)
On entry, the matrix of right or left eigenvectors to be transformed, as returned
by SHSEIN or STREVC. On exit, V is overwritten by the transformed eigenvectors.
LDV (input) INTEGER
The leading dimension of the array V. LDV >= max(1,N).
INFO (output) INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value.
LAPACK version 3.0 15 June 2000 SGEBAK(l)