sggbak.f(3)

NAME
sggbak.f -

SYNOPSIS

  Functions/Subroutines
subroutine sggbak (JOB, SIDE, N, ILO, IHI, LSCALE, RSCALE, M, V, LDV, INFO)
SGGBAK

Function/Subroutine Documentation

  subroutine sggbak (characterJOB, characterSIDE, integerN, integerILO, integerIHI, real, dimension( * )LSCALE, real, dimension( * )RSCALE, integerM, real, dimension( ldv, * )V, integerLDV, integerINFO)

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.

Date:
    November 2011

Further Details:

      See R.C. Ward, Balancing the generalized eigenvalue problem,
                     SIAM J. Sci. Stat. Comp. 2 (1981), 141-152.

Definition at line 147 of file sggbak.f.

Author

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