SRC/sgecon.f(3)

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version 3.12.1 · 4 versions
, in arch rolling

🎀 NAME 🎀

okay so this is SRC/sgecon.f(3) from the Library Functions Manual, and it's literally the page for sgecon — yes bestie, we're doing LAPACK Fortran tea today 💅✨

✨ SYNOPSIS ✨

🧚 Functions/Subroutines 🧚

  • subroutine sgecon (norm, n, a, lda, anorm, rcond, work, iwork, info) — SGECON

🫶 Function/Subroutine Documentation 🫶

🌟 subroutine sgecon 🌟

   subroutine sgecon (character norm, integer n, real, dimension( lda, * ) a,
       integer lda, real anorm, real rcond, real, dimension( * ) work, integer,
       dimension( * ) iwork, integer info)

SGECON

💖 Purpose 💖

okay so SGECON estimates the reciprocal of the condition number of a general real matrix A, in either the 1-norm or the infinity-norm, using the LU factorization computed by SGETRF. no cap, that's the whole vibe 🔥

an estimate is obtained for norm(inv(A)), and the reciprocal of the condition number is computed as:

   RCOND = 1 / ( norm(A) * norm(inv(A)) ).

🍓 Parameters 🍓

🌸 NORM 🌸

NORM is CHARACTER*1 and 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. periodt.

🌸 A 🌸

A is REAL array, dimension (LDA,N), holding the factors L and U from the factorization A = P*L*U as computed by SGETRF.

🌸 LDA 🌸

LDA is INTEGER, the leading dimension of the array A. LDA >= max(1,N).

🌸 ANORM 🌸

ANORM is REAL:

  • if NORM = '1' or 'O', it's the 1-norm of the original matrix A;
  • if NORM = 'I', it's 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/(norm(A) * norm(inv(A))).

🌸 WORK 🌸

WORK is REAL array, dimension (4*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. NaNs are illegal values for ANORM, and they propagate to the output parameter RCOND. Infinity is illegal for ANORM, and it propagates to the output parameter RCOND as 0.
  • = 1: if RCOND = NaN, or RCOND = Inf, or the computed norm of the inverse of A is 0. In the latter, RCOND = 0 is returned.

👑 Author 👑

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

🌈 Definition at line 🌈

Definition at line 130 of file sgecon.f.

💀 Author 💀

Generated automatically by Doxygen for LAPACK from the source code.

that's the whole page, bestie 💖 — LAPACK Version 3.12.0, SRC/sgecon.f(3). mwah 🫶✨

📦 where this page comes from