/home/abui.../chetri2.f(3)

🦋 NAME 🦋

okay so bestie, this is the Library Functions Manual page for /home/abui.../chetri2.f(3). The NAME section is literally just this file path:

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/chetri2.f

No cap, that's the whole NAME block. 💅

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🌸 SYNOPSIS 🌸

Functions/Subroutines

• subroutine CHETRI2 (uplo, n, a, lda, ipiv, work, lwork, info) — the one and only CHETRI2, showing up to do its thing. 🫶

Here's the synopsis line exactly, bestie:

       subroutine CHETRI2 (uplo, n, a, lda, ipiv, work, lwork, info)
           CHETRI2

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🧚 Function/Subroutine Documentation 🧚

Full signature, copied exactly:

   subroutine CHETRI2 (character uplo, integer n, complex, dimension( lda, * )
       a, integer lda, integer, dimension( * ) ipiv, complex, dimension( * )
       work, integer lwork, integer info)
       CHETRI2

🎯 Purpose 🎯

So CHETRI2 computes the inverse of a COMPLEX hermitian indefinite matrix A using the factorization A = U*D*U**T or A = L*D*L**T computed by CHETRF. And listen: CHETRI2 set the LEADING DIMENSION of the workspace before calling CHETRI2X that actually computes the inverse. That's the whole purpose, periodt. ✨

🌈 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. It's the order of matrix A. N >= 0.

A

A is COMPLEX array, dimension (LDA,N). On entry, it's the block diagonal matrix D and the multipliers used to obtain the factor U or L as computed by CHETRF.

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 array A. LDA >= max(1,N).

IPIV

IPIV is INTEGER array, dimension (N). It has the details of the interchanges and the block structure of D as determined by CHETRF.

WORK

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

LWORK

LWORK is INTEGER. It's the dimension of 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 chetri2.f.

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🧚 Author 🧚

Generated automatically by Doxygen for LAPACK from the source code.

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