SRC/slaqz4.f(3)

💖 SRC/slaqz4.f(3) 💖

okay bestie, welcome to SRC/slaqz4.f(3) from the Library Functions Manual. it's giving “we are deep in LAPACK land” and honestly? iconic. this page is all about one subroutine and its whole entourage of arguments. let's go. 💅

---

✨ NAME ✨

SRC/slaqz4.f

🌸 SYNOPSIS 🌸

🎀 Functions/Subroutines 🎀

subroutine slaqz4 (ilschur, ilq, ilz, n, ilo, ihi, nshifts,
           nblock_desired, sr, si, ss, a, lda, b, ldb, q, ldq, z, ldz, qc,
           ldqc, zc, ldzc, work, lwork, info)

SLAQZ4 — yes, that's the main character. 👑

🦋 Function/Subroutine Documentation 🦋

subroutine slaqz4

subroutine slaqz4 (logical, intent(in) ilschur, logical, intent(in) ilq,
       logical, intent(in) ilz, integer, intent(in) n, integer, intent(in) ilo,
       integer, intent(in) ihi, integer, intent(in) nshifts, integer,
       intent(in) nblock_desired, real, dimension( * ), intent(inout) sr, real,
       dimension( * ), intent(inout) si, real, dimension( * ), intent(inout)
       ss, real, dimension( lda, * ), intent(inout) a, integer, intent(in) lda,
       real, dimension( ldb, * ), intent(inout) b, integer, intent(in) ldb,
       real, dimension( ldq, * ), intent(inout) q, integer, intent(in) ldq,
       real, dimension( ldz, * ), intent(inout) z, integer, intent(in) ldz,
       real, dimension( ldqc, * ), intent(inout) qc, integer, intent(in) ldqc,
       real, dimension( ldzc, * ), intent(inout) zc, integer, intent(in) ldzc,
       real, dimension( * ), intent(inout) work, integer, intent(in) lwork,
       integer, intent(out) info)

SLAQZ4 is the name on the cover, and the whole assignment is right there in the purpose. no notes. 🫶

🎯 Purpose

SLAQZ4 Executes a single multishift QZ sweep. that's the plot, that's the moment, periodt. 💖

🎛️ Parameters

• ILSCHUR — ILSCHUR is LOGICAL. Determines whether or not to update the full Schur form.
• ILQ — ILQ is LOGICAL. Determines whether or not to update the matrix Q.
• ILZ — ILZ is LOGICAL. Determines whether or not to update the matrix Z.
• N — N is INTEGER. The order of the matrices A, B, Q, and Z. N >= 0.
• ILO — ILO is INTEGER.
• IHI — IHI is INTEGER.
• NSHIFTS — NSHIFTS is INTEGER. The desired number of shifts to use.
• NBLOCK_DESIRED — NBLOCK_DESIRED is INTEGER. The desired size of the computational windows.
• SR — SR is REAL array. SR contains the real parts of the shifts to use.
• SI — SI is REAL array. SI contains the imaginary parts of the shifts to use.
• SS — SS is REAL array. SS contains the scale of the shifts to use.
• A — A is REAL array, dimension (LDA, N).
• LDA — LDA is INTEGER. The leading dimension of the array A. LDA >= max( 1, N ).
• B — B is REAL array, dimension (LDB, N).
• LDB — LDB is INTEGER. The leading dimension of the array B. LDB >= max( 1, N ).
• Q — Q is REAL array, dimension (LDQ, N).
• LDQ — LDQ is INTEGER.
• Z — Z is REAL array, dimension (LDZ, N).
• LDZ — LDZ is INTEGER.
• QC — QC is REAL array, dimension (LDQC, NBLOCK_DESIRED).
• LDQC — LDQC is INTEGER.
• ZC — ZC is REAL array, dimension (LDZC, NBLOCK_DESIRED).
• LDZC — LDZ is INTEGER. yep, the manpage says LDZ here, not LDZC — keeping it exact, bestie 💀
• WORK — WORK is REAL array, dimension (MAX(1,LWORK)). On exit, if INFO >= 0, WORK(1) returns the optimal LWORK.
• LWORK — LWORK is INTEGER. The dimension of the array WORK. LWORK >= max(1,N). If LWORK = -1, then a workspace query is assumed; the routine only calculates the optimal size of the WORK array, returns this value as the first entry of the WORK array, and no error message related to LWORK is issued by XERBLA.
• INFO — INFO is INTEGER. = 0: successful exit. < 0: if INFO = -i, the i-th argument had an illegal value.

👑 Author

Thijs Steel, KU Leuven

🌸 Date

May 2020

Definition at line 210 of file slaqz4.f.

🌈 Author 🌈

Generated automatically by Doxygen for LAPACK from the source code.

xoxo, LAPACK Version 3.12.0 💖 from SRC/slaqz4.f(3) — date on the page: May 2020. 🎀✨