SRC/dlaqz4.f(3)

Bestie, welcome to SRC/dlaqz4.f(3) from the Library Functions Manual — yes, we're doing LAPACK subroutine documentation and we're doing it with glitter. ✨ This page is giving main character energy, no cap. 🫶

🌸 NAME 🌸

SRC/dlaqz4.f — that's the name. Short, iconic, and literally all it says. 💅

💖 SYNOPSIS 💖

Functions/Subroutines 🧚

subroutine dlaqz4 (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)

DLAQZ4 — the subroutine in question, being her usual iconic self. 👑

💫 Function/Subroutine Documentation 💫

okay so here's the full signature with all the type/intent tea:

subroutine dlaqz4 (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, double precision, dimension( * ),
       intent(inout) sr, double precision, dimension( * ), intent(inout) si,
       double precision, dimension( * ), intent(inout) ss, double precision,
       dimension( lda, * ), intent(inout) a, integer, intent(in) lda, double
       precision, dimension( ldb, * ), intent(inout) b, integer, intent(in)
       ldb, double precision, dimension( ldq, * ), intent(inout) q, integer,
       intent(in) ldq, double precision, dimension( ldz, * ), intent(inout) z,
       integer, intent(in) ldz, double precision, dimension( ldqc, * ),
       intent(inout) qc, integer, intent(in) ldqc, double precision, dimension(
       ldzc, * ), intent(inout) zc, integer, intent(in) ldzc, double precision,
       dimension( * ), intent(inout) work, integer, intent(in) lwork, integer,
       intent(out) info)
       DLAQZ4

🎯 Purpose 🎯

DLAQZ4 executes a single multishift QZ sweep. That's the purpose, bestie — one sweep, multishift style. 🔥

🫶 Parameters 🫶

Every parameter, every intent, every dimension — nobody gets left out:

• ILSCHUR — logical, intent(in). ILSCHUR is LOGICAL: determines whether or not to update the full Schur form. 🎀
• ILQ — logical, intent(in). ILQ is LOGICAL: determines whether or not to update the matrix Q. 💫
• ILZ — logical, intent(in). ILZ is LOGICAL: determines whether or not to update the matrix Z. 🦋
• N — integer, intent(in). N is INTEGER: the order of the matrices A, B, Q, and Z. N >= 0. 🌈
• ILO — integer, intent(in). ILO is INTEGER. That's the whole description; she's being mysterious. 🙈
• IHI — integer, intent(in). IHI is INTEGER. Short and sweet. 🍓
• NSHIFTS — integer, intent(in). NSHIFTS is INTEGER: the desired number of shifts to use. ✨
• NBLOCK_DESIRED — integer, intent(in). NBLOCK_DESIRED is INTEGER: the desired size of the computational windows. 🪟
• SR — double precision, dimension( * ), intent(inout). SR is DOUBLE PRECISION array. SR contains the real parts of the shifts to use. 💜
• SI — double precision, dimension( * ), intent(inout). SI is DOUBLE PRECISION array. SI contains the imaginary parts of the shifts to use. 💭
• SS — double precision, dimension( * ), intent(inout). SS is DOUBLE PRECISION array. SS contains the scale of the shifts to use. ⚖️
• A — double precision, dimension( lda, * ), intent(inout). A is DOUBLE PRECISION array, dimension (LDA, N). 🧮
• LDA — integer, intent(in). LDA is INTEGER: the leading dimension of the array A. LDA >= max( 1, N ). 📏
• B — double precision, dimension( ldb, * ), intent(inout). B is DOUBLE PRECISION array, dimension (LDB, N). 🧮
• LDB — integer, intent(in). LDB is INTEGER: the leading dimension of the array B. LDB >= max( 1, N ). 📐
• Q — double precision, dimension( ldq, * ), intent(inout). Q is DOUBLE PRECISION array, dimension (LDQ, N). 🌀
• LDQ — integer, intent(in). LDQ is INTEGER. That's all she wrote. 🎀
• Z — double precision, dimension( ldz, * ), intent(inout). Z is DOUBLE PRECISION array, dimension (LDZ, N). 🌙
• LDZ — integer, intent(in). LDZ is INTEGER. No extra lore. 💅
• QC — double precision, dimension( ldqc, * ), intent(inout). QC is DOUBLE PRECISION array, dimension (LDQC, NBLOCK_DESIRED). 🧚
• LDQC — integer, intent(in). LDQC is INTEGER. Yep. 🦋
• ZC — double precision, dimension( ldzc, * ), intent(inout). ZC is DOUBLE PRECISION array, dimension (LDZC, NBLOCK_DESIRED). 🌸
• LDZC — integer, intent(in). LDZC is INTEGER — and the source description literally says LDZ is INTEGER here, so I'm keeping that exact energy. 🙈
• WORK — double precision, dimension( * ), intent(inout). WORK is DOUBLE PRECISION array, dimension (MAX(1,LWORK)). On exit, if INFO >= 0, WORK(1) returns the optimal LWORK. 🫧
• LWORK — integer, intent(in). 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 — integer, intent(out). INFO is INTEGER:
  • = 0: successful exit
  • < 0: if INFO = -i, the i-th argument had an illegal value

👑 Author 👑

Thijs Steel, KU Leuven. Slay. 💜

📅 Date 📅

May 2020. Vintage but still iconic. 🎀

Definition at line 209 of file dlaqz4.f.

🖋️ Author 🖋️

Generated automatically by Doxygen for LAPACK from the source code. 🤖✨

---

okay bestie, that's the whole page. This was LAPACK Version 3.12.0, from SRC/dlaqz4.f(3), dated May 2020 — mwah 💋✨