DGTT01(3)

💖 DGTT01(3) 💖

okay bestie, welcome to the LAPACK Library Functions Manual — this page is all about DGTT01 and it came from the dgtt01.f(3) source page. ✨ No cap, we're getting into tridiagonal LU reconstruction and residual math. 💅

🌸 NAME 🌸

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/TESTING/LIN/dgtt01.f

💅 SYNOPSIS 💅

✨ Functions/Subroutines ✨

   subroutine DGTT01 (n, dl, d, du, dlf, df, duf, du2, ipiv, work, ldwork,
       rwork, resid)
       DGTT01

🦋 Function/Subroutine Documentation 🦋

Here's the full signature, character-for-character, because she is iconic:

   subroutine DGTT01 (integer n, double precision, dimension( * ) dl, double
       precision, dimension( * ) d, double precision, dimension( * ) du, double
       precision, dimension( * ) dlf, double precision, dimension( * ) df,
       double precision, dimension( * ) duf, double precision, dimension( * )
       du2, integer, dimension( * ) ipiv, double precision, dimension( ldwork,
       * ) work, integer ldwork, double precision, dimension( * ) rwork, double
       precision resid)
       DGTT01

🎀 Purpose 🎀

DGTT01 reconstructs a tridiagonal matrix A from its LU factorization and computes the residual

   norm(L*U - A) / ( norm(A) * EPS ),

where EPS is the machine epsilon. Obsessed with a clean residual check. 💖

💜 Parameters 💜

• N — N is INTEGER; the order of the matrix A. N >= 0. 🫶
• DL — DL is DOUBLE PRECISION array, dimension (N-1); the (n-1) sub-diagonal elements of A. 🌸
• D — D is DOUBLE PRECISION array, dimension (N); the diagonal elements of A. 💫
• DU — DU is DOUBLE PRECISION array, dimension (N-1); the (n-1) super-diagonal elements of A. 🦋
• DLF — DLF is DOUBLE PRECISION array, dimension (N-1); the (n-1) multipliers that define the matrix L from the LU factorization of A. 💅
• DF — DF is DOUBLE PRECISION array, dimension (N); the n diagonal elements of the upper triangular matrix U from the LU factorization of A. 👑
• DUF — DUF is DOUBLE PRECISION array, dimension (N-1); the (n-1) elements of the first super-diagonal of U. 🌈
• DU2 — DU2 is DOUBLE PRECISION array, dimension (N-2); the (n-2) elements of the second super-diagonal of U. ⭐
• IPIV — IPIV is INTEGER array, dimension (N); the pivot indices; for 1 <= i <= n, row i of the matrix was interchanged with row IPIV(i). IPIV(i) will always be either i or i+1; IPIV(i) = i indicates a row interchange was not required. 🎀
• WORK — WORK is DOUBLE PRECISION array, dimension (LDWORK,N). 🧚
• LDWORK — LDWORK is INTEGER; the leading dimension of the array WORK. LDWORK >= max(1,N). 💜
• RWORK — RWORK is DOUBLE PRECISION array, dimension (N). 🍓
• RESID — RESID is DOUBLE PRECISION; the scaled residual: norm(L*U - A) / (norm(A) * EPS). 🔥

👑 Author 👑

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

Definition at line 132 of file dgtt01.f.

👑 Author 👑

Generated automatically by Doxygen for LAPACK from the source code. 💅

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k bye bestie! The footer says LAPACK, Version 3.12.0, and the path /home/abui...IN/dgtt01.f(3). 🎀💖✨