TESTING/LIN/zgtt01.f(3)

💖 NAME 💖

TESTING/LIN/zgtt01.f — and yes, this is a Library Functions Manual page, bestie. We're in the TESTING/LIN folder and this one is all about zgtt01.

✨ SYNOPSIS ✨

Functions/Subroutines

   subroutine zgtt01 (n, dl, d, du, dlf, df, duf, du2, ipiv, work, ldwork,
       rwork, resid)
       ZGTT01

🧚 Function/Subroutine Documentation 🧚

Here's the full signature, exactly as this page gives it:

   subroutine zgtt01 (integer n, complex*16, dimension( * ) dl, complex*16,
       dimension( * ) d, complex*16, dimension( * ) du, complex*16, dimension(
       * ) dlf, complex*16, dimension( * ) df, complex*16, dimension( * ) duf,
       complex*16, dimension( * ) du2, integer, dimension( * ) ipiv,
       complex*16, dimension( ldwork, * ) work, integer ldwork, double
       precision, dimension( * ) rwork, double precision resid)
       ZGTT01

🎀 Purpose 🎀

Okay so ZGTT01 reconstructs a tridiagonal matrix A from its LU factorization, and then it computes the residual:

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

where EPS is the machine epsilon. That's the whole glow-up: rebuild from LU, then check the residual 💅

🌸 Parameters 🌸

• N — N is INTEGER. It's the order of the matrix A, and N >= 0. No negatives, bestie.
• DL — DL is COMPLEX*16 array, dimension (N-1). These are the (n-1) sub-diagonal elements of A.
• D — D is COMPLEX*16 array, dimension (N). These are the diagonal elements of A.
• DU — DU is COMPLEX*16 array, dimension (N-1). These are the (n-1) super-diagonal elements of A.
• DLF — DLF is COMPLEX*16 array, dimension (N-1). These are the (n-1) multipliers that define the matrix L from the LU factorization of A.
• DF — DF is COMPLEX*16 array, dimension (N). These are the n diagonal elements of the upper triangular matrix U from the LU factorization of A.
• DUF — DUF is COMPLEX*16 array, dimension (N-1). These are the (n-1) elements of the first super-diagonal of U.
• DU2 — DU2 is COMPLEX*16 array, dimension (N-2). These are the (n-2) elements of the second super-diagonal of U.
• IPIV — IPIV is INTEGER array, dimension (N). These are 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 COMPLEX*16 array, dimension (LDWORK,N).
• LDWORK — LDWORK is INTEGER. It's the leading dimension of the array WORK, and LDWORK >= max(1,N).
• RWORK — RWORK is DOUBLE PRECISION array, dimension (N).
• RESID — RESID is DOUBLE PRECISION. This is 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 zgtt01.f.

👑 Author (generated edition) 👑

Generated automatically by Doxygen for LAPACK from the source code.

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And that's the footer tea, bestie ☕: source is LAPACK, version is Version 3.12.0, and the page is TESTING/LIN/zgtt01.f(3). periodt ✨