SRC/zsytri2.f(3)

🦋 SRC/zsytri2.f(3) — Library Functions Manual, but make it a group chat 🦋

okay so bestie, this is the page for SRC/zsytri2.f, and it’s giving “LAPACK subroutine with main character energy.” Let’s go. 💅

---

🌸 NAME 🌸

SRC/zsytri2.f

✨ SYNOPSIS ✨

🧚 Functions/Subroutines 🧚

• subroutine zsytri2 (uplo, n, a, lda, ipiv, work, lwork, info) — ZSYTRI2

👑 Function/Subroutine Documentation 👑

subroutine zsytri2 (character uplo, integer n, complex*16, dimension( lda, * ) a, integer lda, integer, dimension( * ) ipiv, complex*16, dimension( * ) work, integer lwork, integer info)

ZSYTRI2

🎀 Purpose 🎀

okay so ZSYTRI2 computes the inverse of a COMPLEX*16 symmetric indefinite matrix A using the factorization A = U*D*U**T or A = L*D*L**T that was computed by ZSYTRF. Also, ZSYTRI2 sets the LEADING DIMENSION of the workspace before calling ZSYTRI2X, and ZSYTRI2X is the one that actually computes the inverse. periodt. 💖

🍓 Parameters 🍓

• UPLO — UPLO is CHARACTER*1. It says 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*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. iconic. 💅
• LDA — LDA is INTEGER. It’s the leading dimension of the array A. LDA >= max(1,N). 🫶
• IPIV — IPIV is INTEGER array, dimension (N). It holds details of the interchanges and the block structure of D as determined by ZSYTRF. 🔥
• WORK — WORK is COMPLEX*16 array, dimension (N+NB+1)*(NB+3). 🌈
• LWORK — LWORK is INTEGER. It’s the dimension of the array WORK. WORK is size >= (N+NB+1)*(NB+3). If LDWORK = -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 LDWORK 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 ⭐

Definition at line 126 of file zsytri2.f.

🌈 Author 🌈

Generated automatically by Doxygen for LAPACK from the source code.

---

💖 bestie, that’s the whole page. Source/version tea: LAPACK, Version 3.12.0, and the file is SRC/zsytri2.f(3). Mwah 💅