SRC/zsytrs2.f(3)

🌸 SRC/zsytrs2.f(3) — Library Functions Manual 🌸

okay so bestie, you've landed on the SRC/zsytrs2.f(3) page from the Library Functions Manual. It's a LAPACK subroutine page, and it's lowkey iconic: we're solving A*X = B with a complex symmetric matrix A, using a factorization that ZSYTRF computed and ZSYCONV converted. Let's go 💅

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✨ NAME ✨

SRC/zsytrs2.f — that's the name/filename this page is about. Short, sweet, slay.

🎀 SYNOPSIS 🎀

🦋 Functions/Subroutines 🦋

• subroutine zsytrs2 (uplo, n, nrhs, a, lda, ipiv, b, ldb, work, info) — ZSYTRS2

subroutine zsytrs2 (uplo, n, nrhs, a, lda, ipiv, b, ldb, work, info)
    ZSYTRS2

💖 Function/Subroutine Documentation 💖

🌟 subroutine zsytrs2 🌟

Full signature, exactly as the page gives it:

       subroutine zsytrs2 (character uplo, integer n, integer nrhs, complex*16,
              dimension( lda, * ) a, integer lda, integer, dimension( * ) ipiv,
              complex*16, dimension( ldb, * ) b, integer ldb, complex*16, dimension( *
              ) work, integer info)
              ZSYTRS2

🦋 Purpose 🦋

ZSYTRS2 solves a system of linear equations A*X = B with a complex symmetric matrix A using the factorization A = U*D*U**T or A = L*D*L**T computed by ZSYTRF and converted by ZSYCONV.

🌸 Parameters 🌸

• UPLO — a CHARACTER*1 that tells us whether the details of the factorization are stored as an upper or lower triangular matrix. The values are:
  • = 'U': Upper triangular, form is A = U*D*U**T;
  • = 'L': Lower triangular, form is A = L*D*L**T.
• N — INTEGER; the order of the matrix A. Constraint: N >= 0.
• NRHS — INTEGER; the number of right hand sides, i.e., the number of columns of the matrix B. Constraint: NRHS >= 0.
• A — COMPLEX*16 array, dimension (LDA,N); the block diagonal matrix D and the multipliers used to obtain the factor U or L as computed by ZSYTRF.

bestie, heads up: A is input / output, not input-only. This might be counter-intuitive, and one may think that A is input only. But A is input / output. This is because, at the start of the subroutine, we permute A in a form and then we permute A back to its original form at the end. That's the whole tea 🫖.

• LDA — INTEGER; the leading dimension of the array A. Constraint: LDA >= max(1,N).
• IPIV — INTEGER array, dimension (N); details of the interchanges and the block structure of D as determined by ZSYTRF.
• B — COMPLEX*16 array, dimension (LDB,NRHS); on entry, the right hand side matrix B. On exit, the solution matrix X.
• LDB — INTEGER; the leading dimension of the array B. Constraint: LDB >= max(1,N).
• WORK — COMPLEX*16 array, dimension (N).
• INFO — INTEGER; the exit-status bestie:
  • = 0: successful exit
  • < 0: if INFO = -i, the i-th argument had an illegal value

👑 Author 👑

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

Definition at line 130 of file zsytrs2.f.

📜 Author 📜

Generated automatically by Doxygen for LAPACK from the source code.

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footer tea, served cute: source/version is LAPACK Version 3.12.0, and the page/source is SRC/zsytrs2.f(3). The original footer doesn't print a date, so we're not inventing one — no cap, bestie 🙈💜