ZSYTRI(3)

💖 ZSYTRI(3) — bestie manual moment 💖

Okay so this is ZSYTRI(3) from the Library Functions Manual, and the source file is the very long and iconic /home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/zsytri.f. It is giving LAPACK Fortran subroutine energy, and we’re gonna walk through it together, fr fr. 💅

---

✨ NAME ✨

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/zsytri.f — that’s it, that’s the name entry. The full path ate and left no crumbs. 😭

🌸 SYNOPSIS 🌸

Functions/Subroutines

subroutine ZSYTRI (uplo, n, a, lda, ipiv, work, info)

ZSYTRI — the subroutine herself. Main character energy, no cap. 👑

🦋 Function/Subroutine Documentation 🦋

subroutine ZSYTRI (character uplo, integer n, complex*16, dimension( lda, * ) a, integer lda, integer, dimension( * ) ipiv, complex*16, dimension( * ) work, integer info)

ZSYTRI — again, here to do her thing. 🫶

💅 Purpose

ZSYTRI computes the inverse of a complex symmetric indefinite matrix A using the factorization A = U*D*U**T or A = L*D*L**T computed by ZSYTRF.

🎀 Parameters

• UPLO — UPLO is CHARACTER*1; it specifies whether the details of the factorization are stored as an upper or lower triangular matrix. The values are literal:
  • = '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*16 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 ZSYTRF.
  • 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; 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 ZSYTRF.
• WORK — WORK is COMPLEX*16 array, dimension (2*N).
• 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.

Bestie, if INFO > 0 the matrix is singular, so the inverse could not be computed — no cap, that’s literally what the docs say. 💀

👑 Author

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

📍 Definition

Definition at line 113 of file zsytri.f.

🌟 Author

Generated automatically by Doxygen for LAPACK from the source code.

---

Cute little sign-off, bestie: this page is signed by LAPACK Version 3.12.0 and the footer path /home/abui...RC/zsytri.f(3). There’s no separate date in the footer, just that path — so that’s the whole vibe. 💜✨