PZPBTRS(l)

📦 version 1.5, in ubuntu jammy

💖 PZPBTRS 💖

ok so bestie, welcome to PZPBTRS(l) — she's a LAPACK routine, she's version 1.5, she's iconic, and she's here to solve a whole system of linear equations for you. no cap. let's get into it. 🦋

✨ NAME ✨

PZPBTRS — solve a system of linear equations

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

like yes, that's the whole assignment, and she ATE. 💅

🌸 SYNOPSIS 🌸

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

    CHARACTER       UPLO

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

    INTEGER         DESCA( * ), DESCB( * )

    COMPLEX*16      A( * ), AF( * ), B( * ), WORK( * )

look at all those arguments bestie. every single one of them is doing her little job. we love a full cast. 🎀

👑 PURPOSE 👑

PZPBTRS solves a system of linear equations

where A(1:N, JA:JA+N-1) is the matrix used to produce the factors stored in A(1:N,JA:JA+N-1) and AF by PZPBTRF.

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

Depending on the value of UPLO, A stores either U or L in the equn

A(1:N, JA:JA+N-1) = U'*U

or

L*L'

as computed by PZPBTRF.

🚨 bestie. listen. routine PZPBTRF MUST be called first. like, no PZPBTRF first, no vibes. it's giving prerequisites. it's giving "read the room". do not skip her. 😭

that's the whole page, and honestly? she's perfect. go forth and solve your banded symmetric positive definite distributed system, main character. 🌈✨

this has been PZPBTRS(l) from LAPACK version 1.5, dated 12 May 1997 — mwah, love you, bye 🫶💖

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