PSDTTRSV(l)

✨ NAME ✨

okay bestie, meet PSDTTRSV(l) — a LAPACK routine, version 1.5, and she does exactly this:

• PSDTTRSV — solve a tridiagonal 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 🦋

no cap, here's the whole cast list:

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

           CHARACTER        TRANS, UPLO

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

           INTEGER          DESCA( * ), DESCB( * )

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

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🌸 PURPOSE 🌸

PSDTTRSV solves a tridiagonal triangular 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)^T * X = B(IB:IB+N-1, 1:NRHS)

where A(1:N, JA:JA+N-1) is a tridiagonal triangular matrix factor produced by the Gaussian elimination code PS@(dom_pre)TTRF 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)^T is dictated by the user by the parameter TRANS.

Routine PSDTTRF MUST be called first.

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mwah 💋 that's the whole page, bestie. This was LAPACK version 1.5, dated 12 May 1997, and the manual page is PSDTTRSV(l). slay ✨