SRC/dlarfx.f(3)

📦
version 3.12.1 · 4 versions
, in arch rolling

🎀 SRC/dlarfx.f ✨

okay bestie so this is a page from the Library Functions Manual — section 3 obviously — and it's all about one iconic little Fortran subroutine. no cap, she's a whole vibe: dlarfx. 💅

✨ SYNOPSIS ✨

Functions/Subroutines

  • subroutine dlarfx (side, m, n, v, tau, c, ldc, work) — DLARFX applies an elementary reflector to a general rectangular matrix, with loop unrolling when the reflector has order ≤ 10.

💖 Function/Subroutine Documentation 💖

🌸 subroutine dlarfx (character side, integer m, integer n, double precision, dimension( * ) v, double precision tau, double precision, dimension( ldc, * ) c, integer ldc, double precision, dimension( * ) work)

DLARFX applies an elementary reflector to a general rectangular matrix, with loop unrolling when the reflector has order ≤ 10.

🦋 Purpose:

!>
!> DLARFX applies a real elementary reflector H to a real m by n
!> matrix C, from either the left or the right. H is represented in the
!> form
!>
!>       H = I - tau * v * v**T
!>
!> where tau is a real scalar and v is a real vector.
!>
!> If tau = 0, then H is taken to be the unit matrix
!>
!> This version uses inline code if H has order < 11.
!>

like, literally — she takes your real elementary reflector H and slaps it onto a real m by n matrix C, either from the left or the right, your choice, main character energy 🌈. H is living in the form H = I - tau * v * v**T where tau is a real scalar and v is a real vector. and if tau = 0? bestie, H is just the unit matrix, that's it, that's the whole plot. and this version uses inline code if H has order < 11 🔥

👑 Parameters

  • SIDE — SIDE is CHARACTER*1 — = 'L': form H * C — = 'R': form C * H 🫶
  • M — M is INTEGER — The number of rows of the matrix C.
  • N — N is INTEGER — The number of columns of the matrix C.
  • V — V is DOUBLE PRECISION array, dimension (M) if SIDE = 'L' or (N) if SIDE = 'R' — The vector v in the representation of H.
  • TAU — TAU is DOUBLE PRECISION — The value tau in the representation of H.
  • C — C is DOUBLE PRECISION array, dimension (LDC,N) — On entry, the m by n matrix C. On exit, C is overwritten by the matrix H * C if SIDE = 'L', or C * H if SIDE = 'R'. 💀 (yes she will eat your input, that's the point)
  • LDC — LDC is INTEGER — The leading dimension of the array C. LDC >= (1,M).
  • WORK — WORK is DOUBLE PRECISION array, dimension (N) if SIDE = 'L' or (M) if SIDE = 'R' — WORK is not referenced if H has order < 11. 🧚

⭐ Author

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

Definition at line 119 of file dlarfx.f. 📍

💜 Author

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okay that's the whole page bestie, you ate that 🍓 — this cutie was brought to you by LAPACK, Version 3.12.0, and the file is SRC/dlarfx.f(3). go forth and reflect 💅✨🦋

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