SRC/dlauu2.f(3)

📦
version 3.12.1 · 4 versions
, in arch rolling

✨ SRC/dlauu2.f ✨

okay so bestie, let me tell you about this iconic little Fortran file called dlauu2.f — it's from the LAPACK library and it's literally giving main character energy in the linear algebra world. no cap. 🎀

💖 NAME 💖

SRC/dlauu2.f — the source file that's about to become your new obsession 💅

🌸 SYNOPSIS 🌸

Functions/Subroutines

  • subroutine dlauu2 (uplo, n, a, lda, info) — okay so this one DLAUU2 computes the product UUH or LHL, where U and L are upper or lower triangular matrices (unblocked algorithm). it's the whole vibe, fr fr. ✨

Function/Subroutine Documentation

🦋 subroutine dlauu2 (character uplo, integer n, double precision, dimension( lda, * ) a, integer lda, integer info) 🦋

DLAUU2 computes the product UUH or LHL, where U and L are upper or lower triangular matrices (unblocked algorithm). lowkey iconic, highkey essential. 🫶

💜 Purpose 💜

like, let me spill the tea:

!>
!> DLAUU2 computes the product U * U**T or L**T * L, where the triangular
!> factor U or L is stored in the upper or lower triangular part of
!> the array A.
!>
!> If UPLO = 'U' or 'u' then the upper triangle of the result is stored,
!> overwriting the factor U in A.
!> If UPLO = 'L' or 'l' then the lower triangle of the result is stored,
!> overwriting the factor L in A.
!>
!> This is the unblocked form of the algorithm, calling Level 2 BLAS.
!>

so basically it's multiplying a triangular matrix by its transpose — U times U-transpose, or L-transpose times L — depending on which corner your factor is chillin' in. and it overwrites the answer right back into A like a true multitasker. it's the unblocked version, meaning it calls Level 2 BLAS and it's doing the math the honest way, one step at a time. respect. 👑

🎀 Parameters 🎀

UPLO

!>          UPLO is CHARACTER*1
!>          Specifies whether the triangular factor stored in the array A
!>          is upper or lower triangular:
!>          = 'U':  Upper triangular
!>          = 'L':  Lower triangular
!>

this one's the vibe check — it tells the routine which triangle we're working with:

  • 'U' — Upper triangular, periodt. 💅
  • 'L' — Lower triangular, no cap. 🦋

N

!>          N is INTEGER
!>          The order of the triangular factor U or L.  N >= 0.
!>

the order of your triangular factor U or L. and it's gotta be N >= 0, okay? no negative energy allowed here. 😤

A

!>          A is DOUBLE PRECISION array, dimension (LDA,N)
!>          On entry, the triangular factor U or L.
!>          On exit, if UPLO = 'U', the upper triangle of A is
!>          overwritten with the upper triangle of the product U * U**T;
!>          if UPLO = 'L', the lower triangle of A is overwritten with
!>          the lower triangle of the product L**T * L.
!>

so A is a DOUBLE PRECISION array of dimension (LDA,N). on the way in, it's holding your triangular factor U or L. on the way out? it's been transformed — like a full glow-up:

  • if UPLO = 'U', the upper triangle of A gets overwritten with the upper triangle of the product U * U**T ✨
  • if UPLO = 'L', the lower triangle of A gets overwritten with the lower triangle of the product L**T * L 🌈

it's giving transformation arc, honestly. 🧚

LDA

!>          LDA is INTEGER
!>          The leading dimension of the array A.  LDA >= max(1,N).
!>

the leading dimension of the array A. and it's gotta be LDA >= max(1,N) — don't even think about going smaller. 🙈

INFO

!>          INFO is INTEGER
!>          = 0: successful exit
!>          < 0: if INFO = -k, the k-th argument had an illegal value
!>

the receipts, basically:

  • INFO = 0 — successful exit, we ate and left no crumbs 🔥
  • INFO < 0 — if INFO = -k, the k-th argument had an illegal value. oh no bestie, somebody passed something sus. 💀

🌟 Author 🌟

like, the legends who made this happen:

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

absolute icons, all of them. 👑

⭐ Definition ⭐

Definition at line 101 of file dlauu2.f. — go look for yourself, iykyk. 🦋

💫 Author 💫

Generated automatically by Doxygen for LAPACK from the source code. — so you know it's official official.

okay so quick warning bestie — INFO < 0 means somebody messed up an argument, so double-check your inputs before you come crying to me about weird results, mwah 💋

and that's the whole page! this little gem is from LAPACK Version 3.12.0, dated with all the love, and it's the SRC/dlauu2.f(3) manpage — now go forth and call dlauu2 responsibly, bestie. slay. 💖✨🎀

📦 where this page comes from