PCPBSV(l)

📦 version 1.5, in ubuntu jammy

💖 PCPBSV — NAME 💖

okay bestie, listen up, this is PCPBSV from the LAPACK family (that's the l in PCPBSV(l), iykyk), and what it does is solve a system of linear equations

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

like. that's the whole gig. she solves. that's her moment. 👑

✨ SYNOPSIS ✨

SUBROUTINE PCPBSV( UPLO, N, BW, NRHS, A, JA, DESCA, B, IB, DESCB, WORK,
                   LWORK, INFO )

    CHARACTER      UPLO

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

    INTEGER        DESCA( * ), DESCB( * )

    COMPLEX        A( * ), B( * ), WORK( * )

look at all those arguments. so many little guys. each one matters, don't skip any of them 🫶

🌸 PURPOSE 🌸

PCPBSV solves a system of linear equations

where A(1:N, JA:JA+N-1) is an N-by-N complex banded symmetric positive definite distributed matrix with bandwidth BW.

bestie. banded. symmetric. positive definite. that matrix is giving main character energy and she has RULES. 💅

Cholesky factorization is used to factor a reordering of the matrix into L L'.

the way that she reorders the matrix and then factors it into L L'… iconic behaviour honestly ✨

See PCPBTRF and PCPBTRS for details.

fr fr, if you want the deep lore on the factor-and-solve pipeline, PCPBTRF and PCPBTRS are your girls. go read them. 🎀

that's the whole page, bestie — no more sections hiding down here, no cap 💖

this has been LAPACK routine version 1.5, dated 12 May 1997, and yes she is still serving after all these years. 💜 🦋 🎀

📦 where this page comes from