CSYTRI2X(3)

📦 version 3.12.0, in opensuse-leap 16.0

💖 CSYTRI2X(3) 💖

okay so welcome to the Library Functions Manual, bestie — this is the CSYTRI2X(3) page, and it's giving "tiny LAPACK subroutine with a very specific job." 💅

🌸 NAME 🌸

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/csytri2x.f

That's the NAME entry, no cap. The header/footer path is the abbreviated /home/abui.../csytri2x.f(3).

✨ SYNOPSIS ✨

🦋 Functions/Subroutines 🦋

       subroutine CSYTRI2X (uplo, n, a, lda, ipiv, work, nb, info)
           CSYTRI2X

🧚 Function/Subroutine Documentation 🧚

   subroutine CSYTRI2X (character uplo, integer n, complex, dimension( lda, * )
       a, integer lda, integer, dimension( * ) ipiv, complex, dimension(
       n+nb+1,* ) work, integer nb, integer info)
       CSYTRI2X

🎀 Purpose 🎀

the Purpose block says, literally: CSYTRI2X 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 CSYTRF. Yes, it says "real" in the source — I am not editing that, bestie. 🙈

🎀 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 COMPLEX 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 CSYTRF.

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 NNB structure of D as determined by CSYTRF.

🌸 WORK 🌸

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

🌸 NB 🌸

NB is INTEGER. Block size.

🌸 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.
🫶 if INFO > 0, that's the singular situation: D(i,i) = 0, so the inverse could not be computed. Not a slay, but very much in the manual.

🫶 Author 🫶

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

Definition at line 119 of file csytri2x.f.

🫶 Author 🫶 (the auto-generated edition)

Generated automatically by Doxygen for LAPACK from the source code.

okay that's the whole page, bestie. The footer sign-off is LAPACK Version 3.12.0 with /home/abui.../csytri2x.f(3) — and no date is shown in that footer line, so I'm not inventing one. 💖✨

📦 where this page comes from