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zggbak.f(3) LAPACK zggbak.f(3)

zggbak.f -


subroutine zggbak (JOB, SIDE, N, ILO, IHI, LSCALE, RSCALE, M, V, LDV, INFO)
 
ZGGBAK

ZGGBAK
Purpose:
 ZGGBAK 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
 ZGGBAL.
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 ZGGBAL.
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 ZGGBAL.
          1 <= ILO <= IHI <= N, if N > 0; ILO=1 and IHI=0, if N=0.
LSCALE
          LSCALE is DOUBLE PRECISION array, dimension (N)
          Details of the permutations and/or scaling factors applied
          to the left side of A and B, as returned by ZGGBAL.
RSCALE
          RSCALE is DOUBLE PRECISION array, dimension (N)
          Details of the permutations and/or scaling factors applied
          to the right side of A and B, as returned by ZGGBAL.
M
          M is INTEGER
          The number of columns of the matrix V.  M >= 0.
V
          V is COMPLEX*16 array, dimension (LDV,M)
          On entry, the matrix of right or left eigenvectors to be
          transformed, as returned by ZTGEVC.
          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 148 of file zggbak.f.

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Sat Nov 16 2013 Version 3.4.2

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