DLAQR1(3)

💅 DLAQR1(3) 💅

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💖 NAME 💖

This page is for this exact file: /home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/dlaqr1.f 🎀

✨ SYNOPSIS ✨

🧚 Functions/Subroutines

• subroutine DLAQR1 (n, h, ldh, sr1, si1, sr2, si2, v) — DLAQR1 sets a scalar multiple of the first column of the product of 2-by-2 or 3-by-3 matrix H and specified shifts. 💫

🫶 Function/Subroutine Documentation 🫶

   subroutine DLAQR1 (integer n, double precision, dimension( ldh, * ) h,
       integer ldh, double precision sr1, double precision si1, double
       precision sr2, double precision si2, double precision, dimension( * ) v)

DLAQR1 sets a scalar multiple of the first column of the product of 2-by-2 or 3-by-3 matrix H and specified shifts. iconic 💅

🎯 Purpose:

!>
!>      Given a 2-by-2 or 3-by-3 matrix H, DLAQR1 sets v to a
!>      scalar multiple of the first column of the product
!>
!>      (*)  K = (H - (sr1 + i*si1)*I)*(H - (sr2 + i*si2)*I)
!>
!>      scaling to avoid overflows and most underflows. It
!>      is assumed that either
!>
!>              1) sr1 = sr2 and si1 = -si2
!>          or
!>              2) si1 = si2 = 0.
!>
!>      This is useful for starting double implicit shift bulges
!>      in the QR algorithm.
!>

🧾 Parameters

• N — N is INTEGER; order of the matrix H. N must be either 2 or 3. 🎯
• H — H is DOUBLE PRECISION array, dimension (LDH,N); the 2-by-2 or 3-by-3 matrix H in (*). 🦋
• LDH — LDH is INTEGER; the leading dimension of H as declared in the calling procedure. LDH >= N 💖
• SR1 — SR1 is DOUBLE PRECISION ✨
• SI1 — SI1 is DOUBLE PRECISION ✨
• SR2 — SR2 is DOUBLE PRECISION ✨
• SI2 — SI2 is DOUBLE PRECISION; the shifts in (*). 🌸
• V — V is DOUBLE PRECISION array, dimension (N); a scalar multiple of the first column of the matrix K in (*). 👑

👑 Author

• Univ. of Tennessee
• Univ. of California Berkeley
• Univ. of Colorado Denver
• NAG Ltd.

🌟 Contributors:

Karen Braman and Ralph Byers, Department of Mathematics, University of Kansas, USA 💜

Definition at line 120 of file dlaqr1.f. 📌

👑 Author

Generated automatically by Doxygen for LAPACK from the source code. 🧚

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