SRC/cgecon.f(3)

💅 SRC/cgecon.f(3) 💅

okay bestie, welcome to the SRC/cgecon.f page from the Library Functions Manual. This is the CGECON glow-up, and it’s giving “I estimate condition numbers and I’m iconic about it.” 💖

✨ NAME ✨

SRC/cgecon.f — cgecon, the LAPACK subroutine that estimates the reciprocal of the condition number of a general complex matrix. No cap. 🫶

🎀 SYNOPSIS 🎀

🧚 Functions/Subroutines 🧚

• subroutine cgecon (norm, n, a, lda, anorm, rcond, work, rwork, info) — CGECON

subroutine cgecon (character norm, integer n, complex, dimension( lda, * )
       a, integer lda, real anorm, real rcond, complex, dimension( * ) work,
       real, dimension( * ) rwork, integer info)

💖 Function/Subroutine Documentation 💖

🌸 CGECON 🌸

subroutine cgecon (character norm, integer n, complex, dimension( lda, * )
       a, integer lda, real anorm, real rcond, complex, dimension( * ) work,
       real, dimension( * ) rwork, integer info)

🦋 Purpose 🦋

CGECON estimates the reciprocal of the condition number of a general complex matrix A, in either the 1-norm or the infinity-norm, using the LU factorization computed by CGETRF.

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 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 is INTEGER — the order of the matrix A. N >= 0.
• A is COMPLEX array, dimension (LDA,N) — the factors L and U from the factorization A = P*L*U as computed by CGETRF.
• LDA is INTEGER — the leading dimension of the array A. LDA >= max(1,N).
• 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 is REAL — the reciprocal of the condition number of the matrix A, computed as RCOND = 1/(norm(A) * norm(inv(A))).
• WORK is COMPLEX array, dimension (2*N).
• RWORK is REAL array, dimension (2*N).
• INFO is INTEGER — the exit-status tea ☕:
  • = 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 130 of file cgecon.f.

🌈 Author 🌈

Generated automatically by Doxygen for LAPACK from the source code.

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