DTRTI2(3)

💅 dtrti2(3) — bestie, this is the Library Functions Manual entry for it

Okay so welcome to the manpage for DTRTI2, straight out of LAPACK. Buckle up, it's giving linear algebra but make it cute. 🎀

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✨ NAME ✨

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/dtrti2.f

That's the whole name section babe, it's literally just the file path. No cap. 📁

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🌸 SYNOPSIS 🌸

Functions/Subroutines

subroutine DTRTI2 (uplo, diag, n, a, lda, info)
    DTRTI2 computes the inverse of a triangular matrix (unblocked
    algorithm).

So yeah, it inverts a triangular matrix, and it does it the unblocked way. We love a simple queen. 👑

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🦋 Function/Subroutine Documentation 🦋

subroutine DTRTI2 (character uplo, character diag, integer n, double
    precision, dimension( lda, * ) a, integer lda, integer info)

DTRTI2 computes the inverse of a triangular matrix (unblocked algorithm).

💜 Purpose 💜

!>
!> DTRTI2 computes the inverse of a real upper or lower triangular
!> matrix.
!>
!> This is the Level 2 BLAS version of the algorithm.
!>

So it takes a real upper or lower triangular matrix and hands you back its inverse. And the way it does it is the Level 2 BLAS version of the algorithm — that's the vibe, that's the whole vibe. ✨

🍓 Parameters 🍓

UPLO

!>          UPLO is CHARACTER*1
!>          Specifies whether the matrix A is upper or lower triangular.
!>          = 'U':  Upper triangular
!>          = 'L':  Lower triangular
!>

It's a CHARACTER*1, and it tells the routine whether your matrix A is upper or lower triangular. 'U' = upper triangular, 'L' = lower triangular. Pick your fighter. 💅

DIAG

!>          DIAG is CHARACTER*1
!>          Specifies whether or not the matrix A is unit triangular.
!>          = 'N':  Non-unit triangular
!>          = 'U':  Unit triangular
!>

Also CHARACTER*1, and it says whether A is unit triangular or not. 'N' = non-unit triangular, 'U' = unit triangular. Two letters, huge consequences, iykyk. 🫶

N

!>          N is INTEGER
!>          The order of the matrix A.  N >= 0.
!>

INTEGER, and it's the order of the matrix A. Must be N >= 0, so like, no negative orders please, that's not a thing. 🚫

A

!>          A is DOUBLE PRECISION array, dimension (LDA,N)
!>          On entry, the triangular matrix A.  If UPLO = 'U', the
!>          leading n by n upper triangular part of the array A contains
!>          the upper triangular matrix, and the strictly lower
!>          triangular part of A is not referenced.  If UPLO = 'L', the
!>          leading n by n lower triangular part of the array A contains
!>          the lower triangular matrix, and the strictly upper
!>          triangular part of A is not referenced.  If DIAG = 'U', the
!>          diagonal elements of A are also not referenced and are
!>          assumed to be 1.
!>
!>          On exit, the (triangular) inverse of the original matrix, in
!>          the same storage format.
!>

DOUBLE PRECISION array, dimension (LDA,N). On entry it's your triangular matrix A:

• If UPLO = 'U', the leading n by n upper triangular part of A holds the upper triangular matrix, and the strictly lower triangular part of A is not referenced (girl, it's not even looked at 🙈).
• If UPLO = 'L', the leading n by n lower triangular part of A holds the lower triangular matrix, and the strictly upper triangular part of A is not referenced.
• If DIAG = 'U', the diagonal elements of A are also not referenced and are assumed to be 1. Iconic shortcut behaviour honestly. ⭐

On exit? It's the (triangular) inverse of the original matrix, stored in the same storage format. Same layout, new matrix, glow-up complete. ✨

LDA

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

INTEGER, the leading dimension of the array A, and it's gotta satisfy LDA >= max(1,N). Respect the constraint bestie. 📏

INFO

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

INTEGER, the receipts:

• = 0: successful exit, we ate and left no crumbs. 🔥
• < 0: if INFO = -k, the k-th argument had an illegal value. So like, someone passed something cursed. 💀

👑 Author 👑

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

Four whole institutions on the credits, we stan a collaborative effort. 🫶

Definition at line 109 of file dtrti2.f.

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🌈 Author 🌈

Generated automatically by Doxygen for LAPACK from the source code. So nobody hand-wrote this beauty, the robot did it. 🤖✨

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Heads up bestie: everything above is verbatim from the source — including all them !> comment markers and every single bound. Don't come for me if you skimp on LDA >= max(1,N). 💀

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LAPACK, Version 3.12.0 — and the page lives at /home/abui...RC/dtrti2.f(3). That's the whole footer, mwah, bye bestie! 💖🎀🦋