PSPTSV(l)

📦 version 1.5, in ubuntu jammy

💖 PSPTSV(l) 💖

okay bestie, so this is a page from the LAPACK routine manual, version 1.5, and it's about PSPTSV — a whole solver routine. she's giving linear algebra main character energy and honestly? we're obsessed. let's get into it 🫶

✨ NAME ✨

PSPTSV — she solves a system of linear equations, and the system in question is:

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

periodt. that's literally her whole job 💅

✨ SYNOPSIS ✨

the vibe check, in code form 🎀

SUBROUTINE PSPTSV( N, NRHS, D, E, JA, DESCA, B, IB, DESCB, WORK, LWORK,
                   INFO )

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

    INTEGER        DESCA( * ), DESCB( * )

    REAL           B( * ), D( * ), E( * ), WORK( * )

look at all those arguments. she's highkey booked and busy 👑

✨ PURPOSE ✨

okay so here's the tea. PSPTSV solves a system of linear equations

where A(1:N, JA:JA+N-1) is an N-by-N real tridiagonal symmetric positive definite distributed matrix. yes, that's a whole mouthful, and yes, she handles it flawlessly 🦋

to do this, Cholesky factorization is used to factor a reordering of the matrix into L L'. iconic behavior, no notes ✨

if you want the details — the actual how and the why — go peek at PSPTTRF and PSPTTRS. they're her besties and they spill everything 🌸

and that's the whole page, bestie!! this one came straight from LAPACK version 1.5, dated 12 May 1997 — an absolute vintage queen, and she still ate 💖✨🎀

📦 where this page comes from