SGEBAK(3f)

NAME
SGEBAK - the right or left eigenvectors of a real general matrix by backward transformation on the computed eigenvectors of the balanced matrix output by SGEBAL

SYNOPSIS

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( * )

PURPOSE
SGEBAK forms the right or left eigenvectors of a real general matrix by backward transformation on the computed eigenvectors of the balanced matrix output by SGEBAL.

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 SGEBAL.

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.