/home/abui.../ssytri2.f(3)

📦 version 3.12.0, in opensuse-leap 16.0

hey bestie 💖 welcome to the Library Functions Manual page for /home/abui.../ssytri2.f(3) — it's giving LAPACK, it's giving SSYTRI2, and we're gonna read it together. No cap.

🌸 NAME

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/ssytri2.f

✨ SYNOPSIS

🦋 Functions/Subroutines

subroutine SSYTRI2 (uplo, n, a, lda, ipiv, work, lwork, info)

SSYTRI2 — that's the subroutine, main character energy, periodt.

🫶 Function/Subroutine Documentation

subroutine SSYTRI2 (character uplo, integer n, real, dimension( lda, * ) a,
    integer lda, integer, dimension( * ) ipiv, real, dimension( * ) work,
    integer lwork, integer info)

SSYTRI2

🎯 Purpose

okay so here's the tea ☕: SSYTRI2 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. SSYTRI2 sets the LEADING DIMENSION of the workspace before calling SSYTRI2X that actually computes the inverse. literally the setup bestie — SSYTRI2X is the one doing the actual inverse work.

🎀 Parameters

UPLO

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

  • = '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.

A

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

  • On entry: 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, 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. The leading dimension of the array A. LDA >= max(1,N).

IPIV

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

WORK

WORK is REAL array, dimension (N+NB+1)*(NB+3).

LWORK

LWORK is INTEGER. The dimension of the array WORK. WORK is size >= (N+NB+1)*(NB+3). If LWORK = -1, then a workspace query is assumed; the routine calculates:

  • the optimal size of the WORK array, returns this value as the first entry of the WORK array,
  • and no error message related to LWORK is issued by XERBLA.

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.

👑 Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line 126 of file ssytri2.f.

💀 Author

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