SRC/sgtcon.f(3)

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version 3.12.1 · 4 versions
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🌸 SRC/sgtcon.f(3) 🌸

okay bestie, this page comes from the Library Functions Manual — and yes, it's all about SRC/sgtcon.f. 💖

🌟 NAME 🌟

SRC/sgtcon.f — periodt, that's the name on the page.

✨ SYNOPSIS ✨

🧚 Functions/Subroutines 🧚

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

💅 Function/Subroutine Documentation 💅

   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

SGTCON — that's the subroutine, bestie. 💅

🎀 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))). math but make it cute ✨

🍓 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 🌈

Generated automatically by Doxygen for LAPACK from the source code.

💖 that's the whole page, bestie. Sign-off: LAPACK, Version 3.12.0, source SRC/sgtcon.f(3). The footer didn't give me a date, so I'm not inventing one — periodt. 💖

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