PZDTTRS(l)

💖 PZDTTRS(l) — bestie, we're solving systems today 💖

okay so this is the manual page for PZDTTRS(l), a LAPACK routine, version 1.5, and it is genuinely SO much. buckle up, we're doing linear algebra but make it cute. 🦋

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✨ NAME ✨

PZDTTRS — solve a system of linear equations

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

like. that's the whole job. solve the system, serve the look. 💅

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🌸 SYNOPSIS 🌸

SUBROUTINE PZDTTRS( 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*16      AF( * ), B( * ), D( * ), DL( * ), DU( * ), WORK( * )

look at that argument list. seventeen of them. she's committed. 😭

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🎀 PURPOSE 🎀

PZDTTRS solves a system of linear equations

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

and yes bestie, the page literally just says "or" between them like that. we don't ask questions, we report what's on the page. 🙈

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 PZDTTRF.

A(1:N, JA:JA+N-1) is an N-by-N complex tridiagonal diagonally dominant-like distributed matrix. it's giving structured. it's giving parallel. it's giving everything tbh. 🔥

not me dropping the most important rule at the bottom — routine PZDTTRF MUST be called first. like, must must. before PZDTTRS does literally anything. this is not optional, this is not a vibe suggestion, this is the law. 👑

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and that's the whole page, bestie — go forth and factor first 💜

LAPACK version 1.5, 12 May 1997 — yeah she's a vintage icon and she still ate. mwah. 💖✨🎀🫶