SGTT02(3)

Okay so — SGTT02(3) from the Library Functions Manual has entered the chat, and she's here to check residuals like the icon she is. 💅

🌸 NAME 🌸

SGTT02 — source file: /home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/TESTING/LIN/sgtt02.f. That's the whole name section, bestie. No cap. 🫶

✨ SYNOPSIS ✨

🧚 Functions/Subroutines 💅

subroutine SGTT02 (trans, n, nrhs, dl, d, du, x, ldx, b, ldb, resid)

• SGTT02 — the one and only, serving main character energy.

👑 Function/Subroutine Documentation 👑

subroutine SGTT02 (character trans, integer n, integer nrhs, real,
       dimension( * ) dl, real, dimension( * ) d, real, dimension( * ) du,
       real, dimension( ldx, * ) x, integer ldx, real, dimension( ldb, * ) b,
       integer ldb, real resid)

SGTT02 — yes, her again. Obsessed. 💖

🎀 Purpose 🎀

SGTT02 computes the residual for the solution to a tridiagonal system of equations:

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

where EPS is the machine epsilon. The norm used is the 1-norm. Slay. ✨

🍓 Parameters 🍓

💅 TRANS 💅

TRANS is CHARACTER. It specifies the form of the residual, and the options are giving very specific vibes:

= 'N':  B - A    * X  (No transpose)
= 'T':  B - A**T * X  (Transpose)
= 'C':  B - A**H * X  (Conjugate transpose = Transpose)

🌈 N 🌈

N is INTEGER. The order of the matrix A. N >= 0.

🦋 NRHS 🦋

NRHS is INTEGER. The number of right hand sides, i.e., the number of columns of the matrices B and X. NRHS >= 0.

🌸 DL 🌸

DL is REAL array, dimension (N-1). The (n-1) sub-diagonal elements of A.

🎀 D 🎀

D is REAL array, dimension (N). The diagonal elements of A.

💜 DU 💜

DU is REAL array, dimension (N-1). The (n-1) super-diagonal elements of A.

⭐ X ⭐

X is REAL array, dimension (LDX,NRHS). The computed solution vectors X.

🧚 LDX 🧚

LDX is INTEGER. The leading dimension of the array X. LDX >= max(1,N).

🍓 B 🍓

B is REAL array, dimension (LDB,NRHS).

On entry, the right hand side vectors for the system of linear equations.

On exit, B is overwritten with the difference B - op(A)*X. Not me forgetting that — it's literally in the spec. 💀

🌈 LDB 🌈

LDB is INTEGER. The leading dimension of the array B. LDB >= max(1,N).

👑 RESID 👑

RESID is REAL.

norm(B - op(A)*X) / (norm(op(A)) * norm(X) * EPS)

🫶 Author 🫶

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

Definition at line 123 of file sgtt02.f.

👑 Author 👑

Generated automatically by Doxygen for LAPACK from the source code.

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Cute sign-off: LAPACK · Version 3.12.0 · page/source path: /home/abui...IN/sgtt02.f(3) 🫶💖