SGGBAK (3)  Linux Man Pages
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.
SIDESIDE is CHARACTER*1 = 'R': V contains right eigenvectors; = 'L': V contains left eigenvectors.
NN is INTEGER The number of rows of the matrix V. N >= 0.
ILOILO is INTEGER
IHIIHI 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.
LSCALELSCALE 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.
RSCALERSCALE 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.
MM is INTEGER The number of columns of the matrix V. M >= 0.
VV 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.
LDVLDV is INTEGER The leading dimension of the matrix V. LDV >= max(1,N).
INFOINFO is INTEGER = 0: successful exit. < 0: if INFO = i, the ith 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), 141152.
Definition at line 147 of file sggbak.f.
Author
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