SRC/zla_syrcond_x.f(3)

🎀 SRC/zla_syrcond_x.f 🎀

Okay bestie, so this page is from the LAPACK manual, Version 3.12.0 — and it's all about one very specific little function that lives in SRC/zla_syrcond_x.f. Let's get into it 💅

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✨ SYNOPSIS ✨

Functions/Subroutines

• double precision function zla_syrcond_x (uplo, n, a, lda, af, ldaf, ipiv, x, info, work, rwork) — okay so this one computes the infinity norm condition number of op(A)*diag(x) for symmetric indefinite matrices. That's the whole vibe, no cap.

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🦋 Function/Subroutine Documentation 🦋

double precision function zla_syrcond_x (character uplo, integer n,
    complex*16, dimension( lda, * ) a, integer lda, complex*16, dimension(
    ldaf, * ) af, integer ldaf, integer, dimension( * ) ipiv, complex*16,
    dimension( * ) x, integer info, complex*16, dimension( * ) work, double
    precision, dimension( * ) rwork)

So like, to restate the whole thing: zla_syrcond_x computes the infinity norm condition number of op(A)*diag(x) for symmetric indefinite matrices. That's the assignment, and it ate 🔥

🌸 Purpose:

!>
!>    ZLA_SYRCOND_X Computes the infinity norm condition number of
!>    op(A) * diag(X) where X is a COMPLEX*16 vector.
!>

Literally that's it — condition number time, with X being a COMPLEX*16 vector. Periodt.

💖 Parameters

• UPLO — UPLO is CHARACTER*1, and it tells you which triangle of A is chillin' in storage:

!>       = 'U':  Upper triangle of A is stored;
!>       = 'L':  Lower triangle of A is stored.
!>

• N — N is INTEGER, the number of linear equations, i.e. the order of the matrix A. Gotta be N >= 0, bestie.

!>     The number of linear equations, i.e., the order of the
!>     matrix A.  N >= 0.
!>

• A — A is COMPLEX*16 array, dimension (LDA,N). On entry it's just the N-by-N matrix A. Main character energy 💅

!>     On entry, the N-by-N matrix A.
!>

• LDA — LDA is INTEGER, the leading dimension of the array A, and LDA >= max(1,N). Respect the leading dimension or perish 🙈

!>     The leading dimension of the array A.  LDA >= max(1,N).
!>

• AF — AF is COMPLEX*16 array, dimension (LDAF,N). This holds the block diagonal matrix D plus the multipliers used to obtain the factor U or L, exactly as computed by ZSYTRF.

!>     The block diagonal matrix D and the multipliers used to
!>     obtain the factor U or L as computed by ZSYTRF.
!>

• LDAF — LDAF is INTEGER, the leading dimension of the array AF, and LDAF >= max(1,N). Yes it's a different letter from LDA, no they're not the same thing, keep up 🫶

!>     The leading dimension of the array AF.  LDAF >= max(1,N).
!>

• IPIV — IPIV is INTEGER array, dimension (N). It's the details of the interchanges and the block structure of D, as determined by ZSYTRF.

!>     Details of the interchanges and the block structure of D
!>     as determined by ZSYTRF.
!>

• X — X is COMPLEX*16 array, dimension (N), and it's literally the vector X in the formula op(A) * diag(X). Iconic ⭐

!>     The vector X in the formula op(A) * diag(X).
!>

• INFO — INFO is INTEGER, and it's the status report:

!>       = 0:  Successful exit.
!>     i > 0:  The ith argument is invalid.
!>

Ngl, i > 0 means the *i*th argument was invalid — so if INFO comes back positive, something got passed in wrong, and it'll tell you which one.

• WORK — WORK is COMPLEX*16 array, dimension (2*N). Workspace. That's the whole description, it's giving mysterious 🧚

!>     Workspace.
!>

• RWORK — RWORK is DOUBLE PRECISION array, dimension (N). Also workspace, but make it double precision ✨

!>     Workspace.
!>

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👑 Author 👑

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

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🌈 Definition 🌈

Definition at line 130 of file zla_syrcond_x.f.

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This page was generated automatically by Doxygen for LAPACK from the source code — so like, a robot made it, but a very thorough robot 💀

Okay that's the whole page, bestie — go forth and compute those condition numbers 💜

LAPACK · Version 3.12.0 · SRC/zla_syrcond_x.f(3) — mwah, that's a wrap 🎀🦋🌸