SRC/ztrcon.f(3)

💅 NAME

okay so bestie, welcome to the SRC/ztrcon.f(3) page from the Library Functions Manual ✨. This is the ZTRCON subroutine — the one that estimates the reciprocal of the condition number of a triangular matrix A in either the 1-norm or the infinity-norm. Periodt. 💅

✨ SYNOPSIS

🎀 Functions/Subroutines

subroutine ztrcon (norm, uplo, diag, n, a, lda, rcond, work, rwork,
    info)

ZTRCON

🦋 Function/Subroutine Documentation

subroutine ztrcon (character norm, character uplo, character diag, integer
    n, complex*16, dimension( lda, * ) a, integer lda, double precision
    rcond, complex*16, dimension( * ) work, double precision, dimension( * )
    rwork, integer info)

ZTRCON

🌸 Purpose

No cap, ZTRCON estimates the reciprocal of the condition number of a triangular matrix A, in either the 1-norm or the infinity-norm.

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

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

🧚 Parameters

• NORM — NORM is CHARACTER*1. Specifies whether the 1-norm condition number or the infinity-norm condition number is required, bestie:
  • = '1' or 'O': 1-norm;
  • = 'I': Infinity-norm.
• UPLO — UPLO is CHARACTER*1:
  • = 'U': A is upper triangular;
  • = 'L': A is lower triangular.
• DIAG — DIAG is CHARACTER*1:
  • = 'N': A is non-unit triangular;
  • = 'U': A is unit triangular.
• N — N is INTEGER. The order of the matrix A. N >= 0.
• A — A is COMPLEX*16 array, dimension (LDA,N). The triangular matrix A. If UPLO = 'U', the leading N-by-N upper triangular part of the array A contains the upper triangular matrix, and the strictly lower triangular part of A is not referenced. If UPLO = 'L', the leading N-by-N lower triangular part of the array A contains the lower triangular matrix, and the strictly upper triangular part of A is not referenced. If DIAG = 'U', the diagonal elements of A are also not referenced and are assumed to be 1.
• LDA — LDA is INTEGER. The leading dimension of the array A. LDA >= max(1,N).
• RCOND — RCOND is DOUBLE PRECISION. The reciprocal of the condition number of the matrix A, computed as RCOND = 1/(norm(A) * norm(inv(A))).
• WORK — WORK is COMPLEX*16 array, dimension (2*N).
• RWORK — RWORK is DOUBLE PRECISION array, dimension (N).
• INFO — INFO is INTEGER:
  • = 0: successful exit
  • < 0: if INFO = -i, the i-th argument had an illegal value

👑

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

Definition at line 135 of file ztrcon.f.

💖 Author

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okay bestie, that's the whole vibe. footer shoutout: LAPACK Version 3.12.0 and SRC/ztrcon.f(3) — and no date line to report on this one. 💅✨