SGTCON(3)

💖 sgtcon.f(3) — Library Functions Manual 💖

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🎀 NAME 🎀

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/sgtcon.f — the source file for SGTCON, periodt. 💅

✨ SYNOPSIS ✨

Functions/Subroutines

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

👑 Function/Subroutine Documentation 👑

subroutine SGTCON

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

SGTCON

Purpose

SGTCON estimates the reciprocal of the condition number of a real tridiagonal matrix A using the LU factorization as computed by SGTTRF. 🫶

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. 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 REAL array, dimension (N-1). The (n-1) multipliers that define the matrix L from the LU factorization of A as computed by SGTTRF.
• D — D is REAL array, dimension (N). The n diagonal elements of the upper triangular matrix U from the LU factorization of A.
• DU — DU is REAL array, dimension (N-1). The (n-1) elements of the first superdiagonal of U.
• DU2 — DU2 is REAL 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 REAL. 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 REAL. 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 REAL 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 sgtcon.f.

🌸 Author 🌸

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Final footer vibes, bestie: LAPACK Version 3.12.0, source path /home/abui...RC/sgtcon.f(3) — and that's the whole manual. 💅✨