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LAPACK
3.7.0
LAPACK: Linear Algebra PACKage
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subroutine dggbak | ( | character | JOB, |
character | SIDE, | ||
integer | N, | ||
integer | ILO, | ||
integer | IHI, | ||
double precision, dimension( * ) | LSCALE, | ||
double precision, dimension( * ) | RSCALE, | ||
integer | M, | ||
double precision, dimension( ldv, * ) | V, | ||
integer | LDV, | ||
integer | INFO | ||
) |
DGGBAK
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DGGBAK 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 DGGBAL.
[in] | 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 DGGBAL. |
[in] | SIDE | SIDE is CHARACTER*1 = 'R': V contains right eigenvectors; = 'L': V contains left eigenvectors. |
[in] | N | N is INTEGER The number of rows of the matrix V. N >= 0. |
[in] | ILO | ILO is INTEGER |
[in] | IHI | IHI is INTEGER The integers ILO and IHI determined by DGGBAL. 1 <= ILO <= IHI <= N, if N > 0; ILO=1 and IHI=0, if N=0. |
[in] | 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 DGGBAL. |
[in] | 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 DGGBAL. |
[in] | M | M is INTEGER The number of columns of the matrix V. M >= 0. |
[in,out] | V | V is DOUBLE PRECISION array, dimension (LDV,M) On entry, the matrix of right or left eigenvectors to be transformed, as returned by DTGEVC. On exit, V is overwritten by the transformed eigenvectors. |
[in] | LDV | LDV is INTEGER The leading dimension of the matrix V. LDV >= max(1,N). |
[out] | INFO | INFO is INTEGER = 0: successful exit. < 0: if INFO = -i, the i-th argument had an illegal value. |
See R.C. Ward, Balancing the generalized eigenvalue problem, SIAM J. Sci. Stat. Comp. 2 (1981), 141-152.
Definition at line 149 of file dggbak.f.