SRC/cggbak.f(3)

💖 NAME 💖

SRC/cggbak.f — from the Library Functions Manual, bestie. This whole page is about CGGBAK, and it's lowkey iconic. 💅

✨ SYNOPSIS ✨

🎀 Functions/Subroutines 🎀

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

CGGBAK

🦋 Function/Subroutine Documentation 🦋

   subroutine cggbak (character job, character side, integer n, integer ilo,
       integer ihi, real, dimension( * ) lscale, real, dimension( * ) rscale,
       integer m, complex, dimension( ldv, * ) v, integer ldv, integer info)

CGGBAK

🌸 Purpose 🌸

Okay so CGGBAK 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 CGGBAL. That's the whole vibe. 🦋

💅 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 CGGBAL.

• 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 CGGBAL. 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 CGGBAL.
• 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 CGGBAL.
• M — M is INTEGER. The number of columns of the matrix V. M >= 0.
• V — V is COMPLEX array, dimension (LDV,M). On entry, the matrix of right or left eigenvectors to be transformed, as returned by CTGEVC. 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.

🔥 Further Details 🔥

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

Definition at line 146 of file cggbak.f.

🌟 Author 🌟

Generated automatically by Doxygen for LAPACK from the source code.

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💖 That's the whole SRC/cggbak.f(3) page, bestie! Footer tea: LAPACK Version 3.12.0, page SRC/cggbak.f(3). Periodt. 🫶✨