PCDBSV(l)

📦 version 1.5, in ubuntu jammy

💖 PCDBSV 💖 (that's the l LAPACK manual page, bestie)

okay so real talk — this is PCDBSV from the LAPACK routine fam, version 1.5 energy. it's giving linear algebra solver, it's giving distributed matrix, it's giving we do NOT pivot around here. let's get into it 🎀

✨ NAME ✨

PCDBSV — solves a system of linear equations

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

periodt. that's the whole assignment. 💅

🌸 SYNOPSIS 🌸

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

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

    INTEGER        DESCA( * ), DESCB( * )

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

look at all those arguments. thirteen of them. she's high maintenance and we love that for her 🫶

🦋 PURPOSE 🦋

so PCDBSV solves a system of linear equations

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 complex banded, diagonally dominant-like, distributed matrix with bandwidth BWL, BWU. yes bestie, banded — she's got structure, she's not out here being a full dense mess 🌈

Gaussian elimination without pivoting is used to factor a reordering of the matrix into L U. no cap, no pivots, that's the whole bit. 💀

if you want the actual deets on the factorization and the solve, go read PCDBTRF and PCDBTRS. they're the ones doing the heavy lifting iykyk 👑

lowkey important: PCDBSV is just the vibe-curated combo of factor-then-solve. the manpage says to see PCDBTRF and PCDBTRS for details, and bestie, it means it — go look at them. 📚

okay that's the whole page, mwah 💋

this was LAPACK routine version 1.5, dated 12 May 1997. iconic era, honestly. 🎀✨💖🦋🌸

📦 where this page comes from