DPTT01(3)

💖 DPTT01(3) — Library Functions Manual 💖

okay so bestie, this is the DPTT01(3) page from the Library Functions Manual. The header is doing a little echo thing with /home/abui...IN/dptt01.f(3) (yep, it shows up twice up there), and we’re about to get into the whole subroutine lore. 💅

🌸 NAME 🌸

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/TESTING/LIN/dptt01.f

That’s the file path, no cap. 🎀

✨ SYNOPSIS ✨

🦋 Functions/Subroutines 🦋

   subroutine DPTT01 (n, d, e, df, ef, work, resid)
       DPTT01

✨ Function/Subroutine Documentation ✨

   subroutine DPTT01 (integer n, double precision, dimension( * ) d, double
       precision, dimension( * ) e, double precision, dimension( * ) df, double
       precision, dimension( * ) ef, double precision, dimension( * ) work,
       double precision resid)
       DPTT01

💖 Purpose 💖

okay so the main character move: DPTT01 reconstructs a tridiagonal matrix A from its L*D*L' factorization and computes the residual. The exact formula is:

   norm(L*D*L' - A) / ( n * norm(A) * EPS ),

where EPS is the machine epsilon. That’s the whole purpose, periodt. ✨

🌸 Parameters 🌸

• N — INTEGER. The order of the matrix A.
• D — DOUBLE PRECISION array, dimension (N). The n diagonal elements of the tridiagonal matrix A.
• E — DOUBLE PRECISION array, dimension (N-1). The (n-1) subdiagonal elements of the tridiagonal matrix A.
• DF — DOUBLE PRECISION array, dimension (N). The n diagonal elements of the factor L from the L*D*L' factorization of A.
• EF — DOUBLE PRECISION array, dimension (N-1). The (n-1) subdiagonal elements of the factor L from the L*D*L' factorization of A.
• WORK — DOUBLE PRECISION array, dimension (2*N).
• RESID — DOUBLE PRECISION. norm(L*D*L' - A) / (n * norm(A) * EPS).

🎀 Author 🎀

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

Definition at line 90 of file dptt01.f.

👑 Author 👑

Generated automatically by Doxygen for LAPACK from the source code.

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✨ Cute sign-off: the footer says LAPACK Version 3.12.0 and points to /home/abui...IN/dptt01.f(3). There’s no date in the footer, bestie — that’s the whole footer vibe. 💖🫶