SLARFY(3)

📦 version 3.12.0, in opensuse-leap 16.0

💖 NAME 💖

Hey bestie, welcome to the slarfy.f(3) page from the Library Functions Manual — yes, she’s a LAPACK testing/EIG icon, and the path is literally right here:

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/TESTING/EIG/slarfy.f

✨ SYNOPSIS ✨

🧚 Functions/Subroutines 🧚

subroutine SLARFY (uplo, n, v, incv, tau, c, ldc, work)
    SLARFY

🦋 Function/Subroutine Documentation 🦋

subroutine SLARFY (character uplo, integer n, real, dimension( * ) v,
    integer incv, real tau, real, dimension( ldc, * ) c, integer ldc, real,
    dimension( * ) work)

SLARFY

🎀 Purpose 🎀

Okay so <pink>SLARFY</pink> applies an elementary reflector, or Householder matrix, H, to an n x n symmetric matrix C, from both the left and the right. Obsessed.

H is represented in the form:

H = I - tau * v * v'

where tau is a scalar and v is a vector.

If tau is zero, then H is taken to be the unit matrix. Periodt.

🌸 Parameters 🌸

  • UPLO — UPLO is CHARACTER*1. It specifies whether the upper or lower triangular part of the symmetric matrix C is stored.
    • = 'U': Upper triangle
    • = 'L': Lower triangle
  • N — N is INTEGER. The number of rows and columns of the matrix C. N >= 0.
  • V — V is REAL array, dimension (1 + (N-1)*abs(INCV)). The vector v as described above.
  • INCV — INCV is INTEGER. The increment between successive elements of v. INCV must not be zero. Not. Zero. 💀
  • TAU — TAU is REAL. The value tau as described above.
  • C — C is REAL array, dimension (LDC, N). On entry, the matrix C. On exit, C is overwritten by H * C * H'. 🫶
  • LDC — LDC is INTEGER. The leading dimension of the array C. LDC >= max( 1, N ).
  • WORK — WORK is REAL array, dimension (N).

👑 Author 👑

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

Definition at line 107 of file slarfy.f.

💜 Author 💜

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