SRC/sggbak.f(3)

NAME
SRC/sggbak.f

SYNOPSIS

  Functions/Subroutines
subroutine sggbak (job, side, n, ilo, ihi, lscale, rscale, m, v, ldv, info)
SGGBAK

Function/Subroutine Documentation

  subroutine sggbak (character job, character side, integer n, integer ilo, integer ihi, real, dimension( * ) lscale, real, dimension( * ) rscale, integer m, real, dimension( ldv, * ) v, integer ldv, integer info)

SGGBAK

Purpose:

    !>
    !> SGGBAK forms the right or left eigenvectors of a real generalized
    !> eigenvalue problem A*x = lambda*B*x, by backward transformation on
    !> the computed eigenvectors of the balanced pair of matrices output by
    !> SGGBAL.
    !>

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 SGGBAL.
    !>

    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 SGGBAL.
    !>          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 SGGBAL.
    !>

    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 SGGBAL.
    !>

    M

    !>          M is INTEGER
    !>          The number of columns of the matrix V.  M >= 0.
    !>

    V

    !>          V is REAL array, dimension (LDV,M)
    !>          On entry, the matrix of right or left eigenvectors to be
    !>          transformed, as returned by STGEVC.
    !>          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 145 of file sggbak.f.

Author

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