DERRED(3)

💅 NAME

okay so first thing — the NAME section on this one is a whole mood, because it's literally just a path:

/home/abuild/rpmbuild/BUILD/lapack-
static-3.12.0-build/lapack-3.12.0/TESTING/EIG/derred.f

that's derred.f, bestie — this page is the manual for derred.f(3), and yes it's a whole Scenario™ of a path and we're gonna respect it. 🫶

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✨ SYNOPSIS ✨

🦋 Functions/Subroutines

subroutine DERRED (path, nunit)

DERRED — that's the whole vibe, no cap.

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🎀 Function/Subroutine Documentation 🎀

subroutine DERRED (character*3 path, integer nunit)

literally DERRED. iconic. moving on 💅

🌸 Purpose

the !> block straight from the source, bestie, copied exactly so you don't have to squint at it:

!>
!> DERRED tests the error exits for the eigenvalue driver routines for
!> DOUBLE PRECISION matrices:
!>
!> PATH  driver   description
!> ----  ------   -----------
!> SEV   DGEEV    find eigenvalues/eigenvectors for nonsymmetric A
!> SES   DGEES    find eigenvalues/Schur form for nonsymmetric A
!> SVX   DGEEVX   SGEEV + balancing and condition estimation
!> SSX   DGEESX   SGEES + balancing and condition estimation
!> DBD   DGESVD   compute SVD of an M-by-N matrix A
!>       DGESDD   compute SVD of an M-by-N matrix A (by divide and
!>                conquer)
!>       DGEJSV   compute SVD of an M-by-N matrix A where M >= N
!>       DGESVDX  compute SVD of an M-by-N matrix A(by bisection
!>                and inverse iteration)
!>       DGESVDQ  compute SVD of an M-by-N matrix A(with a
!>                QR-Preconditioned )
!>

so what's the tea ☕: DERRED tests the error exits for the eigenvalue driver routines that work on DOUBLE PRECISION matrices. it's the vibe-checker for the error-handling, not the math itself — it's poking the routines to make sure they scream correctly. 🫶

and the PATH / driver / description situation, spelled out so you can match them up:

• SEV → DGEEV → find eigenvalues/eigenvectors for nonsymmetric A
• SES → DGEES → find eigenvalues/Schur form for nonsymmetric A
• SVX → DGEEVX → SGEEV + balancing and condition estimation
• SSX → DGEESX → SGEES + balancing and condition estimation
• DBD → DGESVD → compute SVD of an M-by-N matrix A
• DBD → DGESDD → compute SVD of an M-by-N matrix A (by divide and conquer)
• DBD → DGEJSV → compute SVD of an M-by-N matrix A where M >= N
• DBD → DGESVDX → compute SVD of an M-by-N matrix A(by bisection and inverse iteration)
• DBD → DGESVDQ → compute SVD of an M-by-N matrix A(with a QR-Preconditioned )

(no i did not "fix" the SGEEV / SGEES bits in those descriptions — that's exactly what the source says, character for character, and we do NOT editorialize the sacred text 💀)

🧚 Parameters

• PATH — PATH is CHARACTER*3, and it's the LAPACK path name for the routines to be tested. that's literally it, that's the whole job. 👑
• NUNIT — NUNIT is INTEGER, and it's the unit number for output. i.e. where all the test output goes to gossip. 🍓

both of those are straight from the !> comments, bestie:

!>          PATH is CHARACTER*3
!>          The LAPACK path name for the routines to be tested.
!>

!>          NUNIT is INTEGER
!>          The unit number for output.
!>

👑 Author

shoutout to the whole committee, fr fr:

• Univ. of Tennessee
• Univ. of California Berkeley
• Univ. of Colorado Denver
• NAG Ltd.

Definition at line 69 of file derred.f. — line 69, iconic, no notes. ✨

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🌈 Author (yes, again)

Generated automatically by Doxygen for LAPACK from the source code. so nobody hand-wrote this bad boy, a robot did, and honestly? it ate. 🤖💅

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that's the page, bestie!! this whole thing is from LAPACK, Version 3.12.0, and the footer path reads /home/abui...IG/derred.f(3) — abbreviated and gorgeous, just like the original. go forth and test those error exits. 🦋💜🎀