PDGBSV(l)

📦 version 1.5, in ubuntu jammy

💖 PDGBSV 💖

okay so bestie, welcome to PDGBSV from the LAPACK girlies — routine version 1.5, no cap. ✨

🌸 NAME 🌸

PDGBSV — solve a system of linear equations

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

that's it, that's the whole job. she solves. she slays. 💅

🎀 SYNOPSIS 🎀

SUBROUTINE PDGBSV( N, BWL, BWU, NRHS, A, JA, DESCA, IPIV, B, IB, DESCB,
                   WORK, LWORK, INFO )

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

    INTEGER        DESCA( * ), DESCB( * ), IPIV( * )

    DOUBLE PRECISION A( * ), B( * ), WORK( * )

look at her. thirteen arguments. absolutely iconic. 👑

🦋 PURPOSE 🦋

so like, PDGBSV solves a system of linear equations, bestie — the main character equation itself being

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

where A(1:N, JA:JA+N-1) is an N-by-N real banded distributed matrix with bandwidth BWL, BWU. banded. distributed. living her best life across the grid. 🌈

and the way she does it?? Gaussian elimination with pivoting — she factors a reordering of the matrix into P L U. reordering. pivoting. the whole little choreography. 💃

if you want the actual tea on how that goes down, see PDGBTRF and PDGBTRS for details. 🫶

anyway that's the page!! this was LAPACK routine version 1.5, dated 12 May 1997 — an absolute vintage queen, still serving linear algebra after all these years. 💖✨🎀🦋🌸💅🫶👑🌈⭐

📦 where this page comes from