SRC/slaqz2.f(3)

💖 SRC/slaqz2.f 💖

okay bestie, welcome to the Library Functions Manual page for SRC/slaqz2.f — yes we're doing LAPACK subroutine lore today and it is lowkey iconic. 🦋✨

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🌸 NAME 🌸

SRC/slaqz2.f — that's the name, bestie. Periodt. 💅

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🦋 SYNOPSIS 🦋

✨ Functions/Subroutines ✨

subroutine slaqz2 (ilq, ilz, k, istartm, istopm, ihi, a, lda, b, ldb,
    nq, qstart, q, ldq, nz, zstart, z, ldz)
    SLAQZ2

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💖 Function/Subroutine Documentation 💖

subroutine slaqz2 (logical, intent(in) ilq, logical, intent(in) ilz,
    integer, intent(in) k, integer, intent(in) istartm, integer, intent(in)
    istopm, integer, intent(in) ihi, real, dimension( lda, * ) a, integer,
    intent(in) lda, real, dimension( ldb, * ) b, integer, intent(in) ldb,
    integer, intent(in) nq, integer, intent(in) qstart, real, dimension(
    ldq, * ) q, integer, intent(in) ldq, integer, intent(in) nz, integer,
    intent(in) zstart, real, dimension( ldz, * ) z, integer, intent(in) ldz)

SLAQZ2 — the subroutine name, front and center, bestie. ✨

🎀 Purpose 🎀

SLAQZ2 chases a 2x2 shift bulge in a matrix pencil down a single position. Yes that's the official purpose, and it's giving "main character moves exactly one position at a time" energy. 💅🔥

💅 Parameters 💅

• ILQ — ILQ is LOGICAL. It determines whether or not to update the matrix Q. 🫶
• ILZ — ILZ is LOGICAL. It determines whether or not to update the matrix Z. 🫶
• K — K is INTEGER. Index indicating the position of the bulge. On entry, the bulge is located in (A(k+1:k+2,k:k+1),B(k+1:k+2,k:k+1)). On exit, the bulge is located in (A(k+2:k+3,k+1:k+2),B(k+2:k+3,k+1:k+2)). 🔥
• ISTARTM — ISTARTM is INTEGER. That's all the source gives us, bestie. 💜
• ISTOPM — ISTOPM is INTEGER. Updates to (A,B) are restricted to (istartm:k+3,k:istopm). It is assumed without checking that istartm <= k+1 and k+2 <= istopm. ⚠️
• IHI — IHI is INTEGER. Again, no extra description in the source. 🎀
• A — A is REAL array, dimension (LDA,N). 🌸
• LDA — LDA is INTEGER. The leading dimension of A as declared in the calling procedure. 💖
• B — B is REAL array, dimension (LDB,N). 🌸
• LDB — LDB is INTEGER. The leading dimension of B as declared in the calling procedure. 💖
• NQ — NQ is INTEGER. The order of the matrix Q. 👑
• QSTART — QSTART is INTEGER. Start index of the matrix Q. Rotations are applied to columns k+2-qStart:k+4-qStart of Q. 🌀
• Q — Q is REAL array, dimension (LDQ,NQ). 🌸
• LDQ — LDQ is INTEGER. The leading dimension of Q as declared in the calling procedure. 💖
• NZ — NZ is INTEGER. The order of the matrix Z. 👑
• ZSTART — ZSTART is INTEGER. Start index of the matrix Z. Rotations are applied to columns k+1-qStart:k+3-qStart of Z. 🌀
• Z — Z is REAL array, dimension (LDZ,NZ). 🌸
• LDZ — LDZ is INTEGER. The leading dimension of Q as declared in the calling procedure. (Yes, the source literally says Q here for LDZ; I'm keeping it exactly as written, bestie. 🙈) 💖

👑 Author 👑

Thijs Steel, KU Leuven. 💜

🌈 Date 🌈

May 2020. 🎀

⭐ Definition ⭐

Definition at line 171 of file slaqz2.f. ✨

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👑 Author 👑

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

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💖 That's the whole page, bestie! Cute sign-off: LAPACK Version 3.12.0, source page SRC/slaqz2.f(3), dated May 2020 — mwah! 🎀✨