SSYTRI2X(3)

okay bestie, you're on the SSYTRI2X(3) page from the Library Functions Manual — let's get into it ✨

💅 NAME

SSYTRI2X — the source file path is literally:

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/ssytri2x.f

✨ SYNOPSIS

🎀 Functions/Subroutines

subroutine SSYTRI2X (uplo, n, a, lda, ipiv, work, nb, info)
    SSYTRI2X

🧚 Function/Subroutine Documentation

subroutine SSYTRI2X (character uplo, integer n, real, dimension( lda, * ) a,
       integer lda, integer, dimension( * ) ipiv, real, dimension( n+nb+1,* )
       work, integer nb, integer info)

🎯 Purpose

SSYTRI2X computes the inverse of a real symmetric indefinite matrix A using the factorization A = U*D*U**T or A = L*D*L**T computed by SSYTRF. periodt 💜

🌸 Parameters

UPLO

UPLO is CHARACTER*1. It specifies whether the details of the factorization are stored as an upper or lower triangular matrix. vibe check:

• 'U': Upper triangular, form is A = U*D*U**T;
• 'L': Lower triangular, form is A = L*D*L**T.

N

N is INTEGER. The order of the matrix A. N >= 0. slay ✨

A

A is REAL array, dimension (LDA,N).

On entry, the NNB diagonal matrix D and the multipliers used to obtain the factor U or L as computed by SSYTRF.

On exit, if INFO = 0, the (symmetric) inverse of the original matrix. If UPLO = 'U', the upper triangular part of the inverse is formed and the part of A below the diagonal is not referenced; if UPLO = 'L' the lower triangular part of the inverse is formed and the part of A above the diagonal is not referenced. the details are giving very precise, bestie 🎀

LDA

LDA is INTEGER. The leading dimension of the array A. LDA >= max(1,N). no cap 💛

IPIV

IPIV is INTEGER array, dimension (N). Details of the interchanges and the NNB structure of D as determined by SSYTRF.

WORK

WORK is REAL array, dimension (N+NB+1,NB+3). that's the workspace situation 🫶

NB

NB is INTEGER. Block size. cute little block size moment 🍑

INFO

INFO is INTEGER.

• = 0: successful exit
• < 0: if INFO = -i, the i-th argument had an illegal value
• > 0: if INFO = i, D(i,i) = 0; the matrix is singular and its inverse could not be computed.

okay this one matters: if INFO > 0, that means D(i,i) = 0, so the matrix is singular and its inverse could not be computed. that's not a cute little glitch, that's a real can't-compute moment 💀

👑 Author

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

Definition at line 119 of file ssytri2x.f.

📝 Author

Generated automatically by Doxygen for LAPACK from the source code. the auto-generated author glow-up 🌈

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okay that's the whole page, bestie. cute sign-off: LAPACK Version 3.12.0, and the footer path is /home/abui.../ssytri2x.f(3). The footer doesn't list a date, so I'm not inventing one — fr fr. 🫶💖