ZPTT02(3)

💅 ZPTT02(3) — Library Functions Manual 💅

okay so bestie, welcome to ZPTT02(3) from the Library Functions Manual. This is a LAPACK testing-lin subroutine page, and it's about to explain a residual check like it's the group-chat tea. Let's get into it 🫶

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💖 NAME 💖

The NAME entry points at this source file path:

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/TESTING/LIN/zptt02.f

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✨ SYNOPSIS ✨

🌸 Functions/Subroutines 🌸

• subroutine ZPTT02 — (uplo, n, nrhs, d, e, x, ldx, b, ldb, resid). That's the short version, bestie.
• ZPTT02 — the routine name again, because that's literally what the synopsis shows 💅

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🫶 Function/Subroutine Documentation 🫶

Here's the full signature, exactly as written:

subroutine ZPTT02 (character uplo, integer n, integer nrhs, double
     precision, dimension( * ) d, complex*16, dimension( * ) e, complex*16,
     dimension( ldx, * ) x, integer ldx, complex*16, dimension( ldb, * ) b,
     integer ldb, double precision resid)

And yeah, the page just says ZPTT02 again right after — iconic repetition, no notes 🎀

🎀 Purpose 🎀

The source wraps this in !> Doxygen comments, but the tea is: ZPTT02 computes the residual for the solution to a symmetric tridiagonal system of equations:

RESID = norm(B - A*X) / (norm(A) * norm(X) * EPS),

where EPS is the machine epsilon. periodt 🦋

🌈 Parameters 🌈

• UPLO — CHARACTER*1. Specifies whether the superdiagonal or the subdiagonal of the tridiagonal matrix A is stored. = 'U': E is the superdiagonal of A. = 'L': E is the subdiagonal of A. 💅
• N — INTEGER. The order of the matrix A.
• NRHS — INTEGER. The number of right hand sides, i.e., the number of columns of the matrices B and X. NRHS >= 0.
• D — DOUBLE PRECISION array, dimension (N). The n diagonal elements of the tridiagonal matrix A.
• E — COMPLEX*16 array, dimension (N-1). The (n-1) subdiagonal elements of the tridiagonal matrix A.
• X — COMPLEX*16 array, dimension (LDX,NRHS). The n by nrhs matrix of solution vectors X.
• LDX — INTEGER. The leading dimension of the array X. LDX >= max(1,N).
• B — COMPLEX*16 array, dimension (LDB,NRHS). On entry, the n by nrhs matrix of right hand side vectors B. On exit, B is overwritten with the difference B - A*X.
• LDB — INTEGER. The leading dimension of the array B. LDB >= max(1,N).
• RESID — DOUBLE PRECISION. norm(B - A*X) / (norm(A) * norm(X) * EPS).

👑 Author 👑

The academic icons behind this:

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

📌 Definition at line 114 of file zptt02.f. 📌

👑 Author — auto-generated edition 👑

Generated automatically by Doxygen for LAPACK from the source code.

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okay bestie, that's the whole page. The footer vibe is LAPACK Version 3.12.0 and the abbreviated source path /home/abui...IN/zptt02.f(3). There's no date listed on the page, so I'm not making one up — fr fr. Stay slay, and may your residual always be small 💖✨