DGGBAK(3)

💖 NAME

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/dggbak.f — that's the file this page is about, bestie. No cap, that's the whole NAME tea. 💅

✨ SYNOPSIS

🧚 Functions/Subroutines

subroutine DGGBAK (job, side, n, ilo, ihi, lscale, rscale, m, v, ldv,
           info)
           DGGBAK

🌸 Function/Subroutine Documentation

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

This is the actual subroutine documentation, and it's giving main-character LAPACK energy. 🦋

✨ Purpose:

Bestie, here's the purpose, fr fr: 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. Periodt. 🌈

🎀 Parameters

💅 JOB

• JOB — JOB is CHARACTER*1. It 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.

🌊 SIDE

• SIDE — SIDE is CHARACTER*1.
  • = 'R': V contains right eigenvectors;
  • = 'L': V contains left eigenvectors.

🔢 N

• N — N is INTEGER. The number of rows of the matrix V. N >= 0.

🌀 ILO

• ILO — ILO is INTEGER.

🌀 IHI

• 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.

⚖️ LSCALE

• 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.

⚖️ RSCALE

• 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.

🧮 M

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

🦋 V

• 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.

📏 LDV

• LDV — LDV is INTEGER. The leading dimension of the matrix V. LDV >= max(1,N).

🚨 INFO

• 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 dggbak.f.

🫶 Author

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Okay bestie, that's the whole page — footer tea: LAPACK, Version 3.12.0, and /home/abui...RC/dggbak.f(3) 🎀✨💖