SRC/zgebak.f(3)

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version 3.12.1 · 7 versions
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Okay bestie, welcome to SRC/zgebak.f(3) — the Library Functions Manual page for our fave complex eigenvector backward-transformation subroutine. Buckle up, it’s giving linear algebra but make it cute 💅✨

🌸 NAME 🌸

SRC/zgebak.f — that’s it, that’s the name, minimal queen behavior 💅

✨ SYNOPSIS ✨

Functions/Subroutines

subroutine zgebak (job, side, n, ilo, ihi, scale, m, v, ldv, info)
    ZGEBAK

🦋 Function/Subroutine Documentation 🦋

subroutine zgebak (character job, character side, integer n, integer ilo,
    integer ihi, double precision, dimension( * ) scale, integer m,
    complex*16, dimension( ldv, * ) v, integer ldv, integer info)
    ZGEBAK

🎯 Purpose

Okay so here’s the tea: ZGEBAK forms the right or left eigenvectors of a complex general matrix by backward transformation on the computed eigenvectors of the balanced matrix output by ZGEBAL. That’s the whole purpose, no cap 🫶

🧾 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 ZGEBAL.
  • 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 ZGEBAL. 1 <= ILO <= IHI <= N, if N > 0; ILO=1 and IHI=0, if N=0.
  • SCALE — SCALE is DOUBLE PRECISION array, dimension (N). Details of the permutation and scaling factors, as returned by ZGEBAL.
  • M — M is INTEGER. The number of columns of the matrix V. M >= 0.
  • V — V is COMPLEX*16 array, dimension (LDV,M). On entry, the matrix of right or left eigenvectors to be transformed, as returned by ZHSEIN or ZTREVC. On exit, V is overwritten by the transformed eigenvectors.
  • LDV — LDV is INTEGER. The leading dimension of the array 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.

Definition at line 129 of file zgebak.f.

🪄 Author

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