SRC/ssytri.f(3)

💖 NAME

SRC/ssytri.f — bestie, this is the Library Functions Manual page for the ssytri subroutine, and it's lowkey iconic. No cap.

✨ SYNOPSIS

🧚 Functions/Subroutines

subroutine ssytri (uplo, n, a, lda, ipiv, work, info)
           SSYTRI

🌸 Function/Subroutine Documentation

🦋 subroutine ssytri

subroutine ssytri (character uplo, integer n, real, dimension( lda, * ) a,
       integer lda, integer, dimension( * ) ipiv, real, dimension( * ) work,
       integer info)
       SSYTRI

💡 Purpose

okay so SSYTRI 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. That's the whole flex, and honestly? It ate. 💅

🌈 Parameters

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

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

N — N is INTEGER. It's the order of the matrix A. The rule is N >= 0, bestie. ✨

A — A is REAL array, dimension (LDA,N). Here's the tea:

• On entry, it holds the block diagonal matrix D and the multipliers used to obtain the factor U or L as computed by SSYTRF.
• On exit, if INFO = 0, it's 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.

LDA — LDA is INTEGER. It's the leading dimension of the array A, and it must satisfy LDA >= max(1,N). periodt. 🎀

IPIV — IPIV is INTEGER array, dimension (N). It carries the details of the interchanges and the block structure of D as determined by SSYTRF. iykyk. 🦋

WORK — WORK is REAL array, dimension (N). That's the whole note, no extra lore. 🌸

INFO — INFO is INTEGER, and it's the vibe check at the end:

• = 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. 💀

👑 Author

Shoutout to the authors, fr fr:

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

Definition at line 113 of file ssytri.f.

🌸 Author

Generated automatically by Doxygen for LAPACK from the source code. Yes, the Doxygen machine did its thing. 🤖💖

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xoxo, LAPACK 💖 — Version 3.12.0, from SRC/ssytri.f(3). bye bestie 🫶