PDDTSV(l)

📦 version 1.5, in ubuntu jammy

✨ PDDTSV ✨ (that's a LAPACK routine bestie, version 1.5, she's a whole linear-algebra icon 💅)

🌸 NAME 🌸

PDDTSV — okay so she solves a system of linear equations, and the system is:

A(1:N, JA:JA+N-1) * X = B(IB:IB+N-1, 1:NRHS)

That's it, that's the job, no cap. 🫶

🎀 SYNOPSIS 🎀

SUBROUTINE PDDTSV( N, NRHS, DL, D, DU, JA, DESCA, B, IB, DESCB, WORK,
                   LWORK, INFO )

    INTEGER        IB, INFO, JA, LWORK, N, NRHS

    INTEGER        DESCA( * ), DESCB( * )

    DOUBLE PRECISION B( * ), D( * ), DL( * ), DU( * ), WORK( * )

Look at that argument list, she's serving range 💖 every single one of those bad boys is doing her job, not one of them is filler.

🔥 PURPOSE 🔥

Okay bestie, so here's the tea. PDDTSV solves a system of linear equations

where A(1:N, JA:JA+N-1) is an N-by-N real tridiagonal diagonally dominant-like distributed matrix. ✨ Yes, distributed. She's not a local girl, she travels. 🌈

Gaussian elimination without pivoting is used to factor a reordering of the matrix into L U. So like, no pivoting, okay? That's the vibe, that's the whole method, we're not switching it up. 😤

💀 Not me about to forget the most important part: See PDDTTRF and PDDTTRS for details. Those are her sisters, go say hi, they have the lore. 🫶

Mwah 💋 that's the page! Sending you off with the receipts: this is from LAPACK version 1.5, dated 12 May 1997 — yes she's an elder but she's still THAT girl, main character energy since '97, periodt. 👑

📦 where this page comes from