SSYT01_ROOK(3)

💅 NAME 💅

okay so bestie, this page is from the TESTING/LI...yt01_rook.f(3) corner of the Library Functions Manual — it's literally the manpage for TESTING/LIN/ssyt01_rook.f, and the whole vibe is "let me reconstruct your symmetric indefinite matrix and check my work." 🎀

✨ SYNOPSIS ✨

🦋 Functions/Subroutines

subroutine ssyt01_rook (uplo, n, a, lda, afac, ldafac, ipiv, c, ldc,
    rwork, resid)

SSYT01_ROOK — that's the whole name, no notes, periodt. 💅

👑 Function/Subroutine Documentation 👑

subroutine ssyt01_rook (character uplo, integer n, real, dimension( lda, * )
    a, integer lda, real, dimension( ldafac, * ) afac, integer ldafac,
    integer, dimension( * ) ipiv, real, dimension( ldc, * ) c, integer ldc,
    real, dimension( * ) rwork, real resid)

SSYT01_ROOK

🌸 Purpose 🌸

!> !> SSYT01_ROOK reconstructs a symmetric indefinite matrix A from its !> block L*D*L' or U*D*U' factorization and computes the residual !> !> !> norm( C - A ) / ( N * norm(A) * EPS ),

hmm wait bestie let me redo that so the code stays exactly code:

!>
!> SSYT01_ROOK reconstructs a symmetric indefinite matrix A from its
!> block L*D*L' or U*D*U' factorization and computes the residual
!>    norm( C - A ) / ( N * norm(A) * EPS ),
!> where C is the reconstructed matrix and EPS is the machine epsilon.
!>

so basically C is the reconstructed matrix and EPS is the machine epsilon — it's giving "did we actually rebuild A correctly or did we fumble it" ✨

🧚 Parameters 🧚

---

• UPLO — UPLO is CHARACTER*1. it says whether we're storing the upper or lower triangular part of the symmetric matrix A. the options, no cap:
  • = 'U': Upper triangular
  • = 'L': Lower triangular
• N — N is INTEGER. the number of rows and columns of the matrix A. the rule is N >= 0. that's it, that's the math 🫶
• A — A is REAL array, dimension (LDA,N). it's lowkey the original symmetric matrix A. the main character, honestly.
• LDA — LDA is INTEGER. the leading dimension of the array A, and it's gotta be LDA >= max(1,N). don't skip this one 🙈
• AFAC — AFAC is REAL array, dimension (LDAFAC,N). this is the factored form of the matrix A. AFAC contains the block diagonal matrix D and the multipliers used to obtain the factor L or U from the block L*D*L' or U*D*U' factorization, as computed by SSYTRF_ROOK. iconic handoff tbh 🔥
• LDAFAC — LDAFAC is INTEGER. the leading dimension of the array AFAC, and yes bestie it needs LDAFAC >= max(1,N). 💀
• IPIV — IPIV is INTEGER array, dimension (N). the pivot indices from SSYTRF_ROOK. 🎀
• C — C is REAL array, dimension (LDC,N). that's all she says. no notes. 💅
• LDC — LDC is INTEGER. the leading dimension of the array C, and yup, LDC >= max(1,N). 🌈
• RWORK — RWORK is REAL array, dimension (N). short and sweet. ⭐
• RESID — RESID is REAL. here's the tea:
  • If UPLO = 'L', it's norm(L*D*L' - A) / ( N * norm(A) * EPS )
  • If UPLO = 'U', it's norm(U*D*U' - A) / ( N * norm(A) * EPS )

literally the whole point of the routine, and it's serving the results. 👑

💖 Author 💖

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line 122 of file ssyt01_rook.f. 🦋

🎀 Author 🎀

Generated automatically by Doxygen for LAPACK from the source code. (yes, a robot wrote the manpage, we're just here to make it cute 😭)

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okay bestie that's the whole page — every flag, every dimension, every >= max(1,N), all of it, untouched. now go forth and residual-check responsibly 💜

LAPACK · Version 3.12.0 · TESTING/LI...yt01_rook.f(3) — mwah, catch you in the next manpage 💅✨🍓