TESTING/LIN/zgbt01.f(3)

💅 NAME 💅

TESTING/LIN/zgbt01.f — bestie, this is the page for that file, and it’s chillin’ in the Library Functions Manual (page label: TESTING/LIN/zgbt01.f(3)). We’re about to get into the ZGBT01 subroutine, and yes, it’s giving main-character linear-algebra energy. ✨

🌸 SYNOPSIS 🌸

🎀 Functions/Subroutines 🎀

subroutine zgbt01 (m, n, kl, ku, a, lda, afac, ldafac, ipiv, work,
    resid)

ZGBT01 — that’s the subroutine name, and it’s literally the whole point of this page. 💖

🦋 Function/Subroutine Documentation 🦋

subroutine zgbt01 (integer m, integer n, integer kl, integer ku, complex*16,
    dimension( lda, * ) a, integer lda, complex*16, dimension( ldafac, * )
    afac, integer ldafac, integer, dimension( * ) ipiv, complex*16,
    dimension( * ) work, double precision resid)

ZGBT01 — okay so this is the full signature situation, and we are obsessed with how specific it is. 💅

💖 Purpose 💖

ZGBT01 reconstructs a band matrix A from its L*U factorization and computes the residual:

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

where EPS is the machine epsilon.

The expression L*U - A is computed one column at a time, so A and AFAC are not modified. No cap. 🫶

🍓 Parameters 🍓

• M — M is INTEGER; the number of rows of the matrix A. M >= 0.
• N — N is INTEGER; the number of columns of the matrix A. N >= 0.
• KL — KL is INTEGER; the number of subdiagonals within the band of A. KL >= 0.
• KU — KU is INTEGER; the number of superdiagonals within the band of A. KU >= 0.
• A — A is COMPLEX*16 array, dimension (LDA,N); the original matrix A in band storage, stored in rows 1 to KL+KU+1.
• LDA — LDA is INTEGER. The leading dimension of the array A. LDA >= max(1,KL+KU+1).
• AFAC — AFAC is COMPLEX*16 array, dimension (LDAFAC,N); the factored form of the matrix A. AFAC contains the banded factors L and U from the L*U factorization, as computed by ZGBTRF. U is stored as an upper triangular band matrix with KL+KU superdiagonals in rows 1 to KL+KU+1, and the multipliers used during the factorization are stored in rows KL+KU+2 to 2*KL+KU+1. See ZGBTRF for further details.
• LDAFAC — LDAFAC is INTEGER; the leading dimension of the array AFAC. LDAFAC >= max(1,2*KL*KU+1).
• IPIV — IPIV is INTEGER array, dimension (min(M,N)); the pivot indices from ZGBTRF.
• WORK — WORK is COMPLEX*16 array, dimension (2*KL+KU+1).
• RESID — RESID is DOUBLE PRECISION; norm(L*U - A) / ( N * norm(A) * EPS ).

👑 Author 👑

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

Definition at line 124 of file zgbt01.f.

💜 Author 💜

Generated automatically by Doxygen for LAPACK from the source code.

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xoxo, your Unix bestie 💖 — source/version: LAPACK Version 3.12.0, page: TESTING/LIN/zgbt01.f(3). Stay reconstructed, bestie! 💅✨