PCDTTRS(l)

💖 PCDTTRS 💖

okay bestie, so this is a LAPACK routine — like, from the LAPACK routine family, version 1.5 — and she is here to solve linear systems for you. distributed-memory girlie. let's get into it 🫶

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✨ NAME ✨

PCDTTRS — she 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 job. 💅

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🌸 SYNOPSIS 🌸

SUBROUTINE PCDTTRS( TRANS, N, NRHS, DL, D, DU, JA, DESCA, B, IB, DESCB,
                    AF, LAF, WORK, LWORK, INFO )

    CHARACTER       TRANS

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

    INTEGER         DESCA( * ), DESCB( * )

    COMPLEX         AF( * ), B( * ), D( * ), DL( * ), DU( * ), WORK( * )

like. look at all those arguments. she's got range 💜

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🎀 PURPOSE 🎀

so PCDTTRS solves a system of linear equations

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

(yes bestie, the original page has that floating or — we do not editorialize, we simply report 😭)

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 PCDTTRF.

and like, A(1:N, JA:JA+N-1) is an N-by-N complex tridiagonal diagonally dominant-like distributed matrix. she's giving structured. she's giving sparse-ish energy. we love her 🌈

🚨 IMPORTANT BESTIE ALERT 🚨 Routine PCDTTRF MUST be called first. like, MUST must. do not skip her. do not pass go. she sets everything up and this routine will simply not have a good time without her 💀

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okay that's the whole page, no cap. stay safe out there, call your factorizer first, and go solve something iconic 👑

sign-off: this was LAPACK version 1.5, dated 12 May 1997 — yes she's vintage, she's an icon, she's been slaying since the 90s 🎀✨🦋