DGTCON(3)

🎀 NAME 🎀

Okay so this is the dgtcon.f(3) page from the Library Functions Manual, bestie — folding that manual-name info right in here so we don't copy the header line like a boring person. The file is literally:

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/dgtcon.f

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✨ SYNOPSIS ✨

🧚 Functions/Subroutines 🧚

• subroutine DGTCON (norm, n, dl, d, du, du2, ipiv, anorm, rcond, work, iwork, info) — DGTCON

subroutine DGTCON (norm, n, dl, d, du, du2, ipiv, anorm, rcond, work,
    iwork, info)

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🌸 Function/Subroutine Documentation 🌸

💅 subroutine DGTCON 💅

subroutine DGTCON (character norm, integer n, double precision, dimension( *
) dl, double precision, dimension( * ) d, double precision, dimension( *
) du, double precision, dimension( * ) du2, integer, dimension( * )
ipiv, double precision anorm, double precision rcond, double precision,
dimension( * ) work, integer, dimension( * ) iwork, integer info)

DGTCON

🦋 Purpose 🦋

DGTCON estimates the reciprocal of the condition number of a real tridiagonal matrix A using the LU factorization as computed by DGTTRF.

An estimate is obtained for norm(inv(A)), and the reciprocal of the condition number is computed as RCOND = 1 / (ANORM * norm(inv(A))).

🎀 Parameters 🎀

• NORM — NORM is CHARACTER*1. It specifies whether the 1-norm condition number or the infinity-norm condition number is required: = '1' or 'O': 1-norm; = 'I': Infinity-norm.
• N — N is INTEGER. The order of the matrix A. N >= 0.
• DL — DL is DOUBLE PRECISION array, dimension (N-1). The (n-1) multipliers that define the matrix L from the LU factorization of A as computed by DGTTRF.
• D — D is DOUBLE PRECISION array, dimension (N). The n diagonal elements of the upper triangular matrix U from the LU factorization of A.
• DU — DU is DOUBLE PRECISION array, dimension (N-1). The (n-1) elements of the first superdiagonal of U.
• DU2 — DU2 is DOUBLE PRECISION array, dimension (N-2). The (n-2) elements of the second superdiagonal 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.
• ANORM — ANORM is DOUBLE PRECISION. If NORM = '1' or 'O', the 1-norm of the original matrix A. If NORM = 'I', the infinity-norm of the original matrix A.
• RCOND — RCOND is DOUBLE PRECISION. The reciprocal of the condition number of the matrix A, computed as RCOND = 1/(ANORM * AINVNM), where AINVNM is an estimate of the 1-norm of inv(A) computed in this routine.
• WORK — WORK is DOUBLE PRECISION array, dimension (2*N).
• IWORK — IWORK is INTEGER array, dimension (N).
• INFO — INFO is INTEGER. = 0: successful exit. < 0: if INFO = -i, the i-th argument had an illegal value.

💜 Author 💜

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

Definition at line 144 of file dgtcon.f.

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🌈 Author 🌈

Generated automatically by Doxygen for LAPACK from the source code.

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Sign-off vibes: LAPACK Version 3.12.0 · /home/abui...RC/dgtcon.f(3) — and that's the whole page, bestie 💅✨