SGGBAK(3)

💅 SGGBAK(3): Library Functions Manual ✨

💖 NAME

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/sggbak.f

okay bestie, that whole path is literally the NAME for this entry — no extra summary, just the .f file glow-up 💅

🌸 SYNOPSIS

🧚 Functions/Subroutines

   Functions/Subroutines
       subroutine SGGBAK (job, side, n, ilo, ihi, lscale, rscale, m, v, ldv,
           info)
           SGGBAK

✨ Function/Subroutine Documentation

   subroutine SGGBAK (character job, character side, integer n, integer ilo,
       integer ihi, real, dimension( * ) lscale, real, dimension( * ) rscale,
       integer m, real, dimension( ldv, * ) v, integer ldv, integer info)
       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. it’s giving “put the eigenvectors back where they belong” energy 🔥

🎀 Parameters

• JOB — 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.
• SIDE — CHARACTER*1. = 'R': V contains right eigenvectors; = 'L': V contains left eigenvectors.
• N — INTEGER. The number of rows of the matrix V. N >= 0.
• ILO — INTEGER.
• IHI — INTEGER. The integers ILO and IHI determined by SGGBAL. 1 <= ILO <= IHI <= N, if N > 0; ILO=1 and IHI=0, if N=0.
• LSCALE — 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.
• RSCALE — 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.
• M — INTEGER. The number of columns of the matrix V. M >= 0.
• V — 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.
• LDV — INTEGER. The leading dimension of the matrix V. LDV >= max(1,N).
• INFO — 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 sggbak.f.

💖 Author

Generated automatically by Doxygen for LAPACK from the source code.

---

LAPACK Version 3.12.0 — source page /home/abui...RC/sggbak.f(3) — date: not shown in the original footer, so no invented date here, bestie 💖