PZDBTRSV(l)

okay so bestie, welcome to PZDBTRSV(l) — she's a LAPACK routine, version 1.5, and she's lowkey iconic. this page is all about solving a banded triangular system, and the vibes are immaculate. 💖✨

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🎀 NAME 🎀

• PZDBTRSV — solve a banded triangular system of linear equations A(1:N, JA:JA+N-1) * X = B(IB:IB+N-1, 1:NRHS) ✨

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✨ SYNOPSIS ✨

the cast list, bestie, and yes she's serving:

       SUBROUTINE PZDBTRSV( UPLO, TRANS, N, BWL, BWU, NRHS, A, JA, DESCA, B,
                            IB, DESCB, AF, LAF, WORK, LWORK, INFO )

           CHARACTER        TRANS, UPLO

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

           INTEGER          DESCA( * ), DESCB( * )

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

every single argument is right there, no skips, periodt. 💅

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💖 PURPOSE 💖

PZDBTRSV solves a banded triangular system of linear equations — either

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

or

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

where A(1:N, JA:JA+N-1) is a banded triangular matrix factor produced by the Gaussian elimination code PZ@(dom_pre)BTRF and is stored in A(1:N,JA:JA+N-1) and AF.

The matrix stored in A(1:N, JA:JA+N-1) is either upper or lower triangular according to UPLO, and the choice of solving A(1:N, JA:JA+N-1) or A(1:N, JA:JA+N-1)^H is dictated by the user by the parameter TRANS.

🚨 bestie, routine PZDBTRF MUST be called first. no cap, do not skip her. 💀

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xoxo, this was LAPACK version 1.5, dated 12 May 1997 💅✨🦋