SRC/checon_3.f(3)

💖 SRC/checon_3.f(3) — Library Functions Manual 💖

okay bestie, this is the Library Functions Manual page for SRC/checon_3.f(3) — and it’s literally all about the checon_3 subroutine, aka CHECON_3. no cap, let’s get into it 💅

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🌸 NAME 🌸

SRC/checon_3.f — the page for the checon_3 subroutine, CHECON_3.

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✨ SYNOPSIS ✨

Functions/Subroutines

subroutine checon_3 (uplo, n, a, lda, e, ipiv, anorm, rcond, work, info)
    CHECON_3

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💅 Function/Subroutine Documentation 💅

okay so here’s the full signature, bestie — look at all these arguments serving looks:

subroutine checon_3 (character uplo, integer n, complex, dimension( lda, * )
a, integer lda, complex, dimension( * ) e, integer, dimension( * ) ipiv,
real anorm, real rcond, complex, dimension( * ) work, integer info)
    CHECON_3

🎯 Purpose 🎯

CHECON_3 estimates the reciprocal of the condition number — in the 1-norm — of a complex Hermitian matrix A using the factorization computed by CHETRF_RK or CHETRF_BK:

A = P*U*D*(U**H)*(P**T) or A = P*L*D*(L**H)*(P**T),

where U (or L) is unit upper (or lower) triangular matrix, U**H (or L**H) is the conjugate of U (or L), P is a permutation matrix, P**T is the transpose of P, and D is Hermitian and block diagonal with 1-by-1 and 2-by-2 diagonal blocks.

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

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

This routine uses BLAS3 solver CHETRS_3. bestie, it’s giving linear algebra royalty 👑

🎀 Parameters 🎀

• UPLO — CHARACTER*1. Specifies whether the details of the factorization are stored as an upper or lower triangular matrix:
  • = 'U': Upper triangular, form is A = P*U*D*(U**H)*(P**T);
  • = 'L': Lower triangular, form is A = P*L*D*(L**H)*(P**T).
• N — INTEGER. The order of the matrix A. N >= 0.
• A — COMPLEX array, dimension (LDA,N). Diagonal of the block diagonal matrix D and factors U or L as computed by CHETRF_RK and CHETRF_BK:
  • a) ONLY diagonal elements of the Hermitian block diagonal matrix D on the diagonal of A, i.e. D(k,k) = A(k,k); (superdiagonal (or subdiagonal) elements of D should be provided on entry in array E), and
  • b) If UPLO = 'U': factor U in the superdiagonal part of A. If UPLO = 'L': factor L in the subdiagonal part of A.
• LDA — INTEGER. The leading dimension of the array A. LDA >= max(1,N).
• E — COMPLEX array, dimension (N). On entry, contains the superdiagonal (or subdiagonal) elements of the Hermitian block diagonal matrix D with 1-by-1 or 2-by-2 diagonal blocks, where:
  • If UPLO = 'U': E(i) = D(i-1,i),i=2:N, E(1) not referenced;
  • If UPLO = 'L': E(i) = D(i+1,i),i=1:N-1, E(N) not referenced.

NOTE: For 1-by-1 diagonal block D(k), where 1 <= k <= N, the element E(k) is not referenced in both UPLO = 'U' or UPLO = 'L' cases.

• IPIV — INTEGER array, dimension (N). Details of the interchanges and the block structure of D as determined by CHETRF_RK or CHETRF_BK.
• ANORM — REAL. The 1-norm of the original matrix A.
• RCOND — 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 — COMPLEX array, dimension (2*N).
• INFO — 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.

🧚 Contributors 🧚

• June 2017, Igor Kozachenko, Computer Science Division, University of California, Berkeley
• September 2007, Sven Hammarling, Nicholas J. Higham, Craig Lucas, School of Mathematics, University of Manchester

📍 Definition 📍

Definition at line 164 of file checon_3.f.

🐣 Author 🐣

Generated automatically by Doxygen for LAPACK from the source code.

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that’s the whole page, bestie! 💖 the footer says LAPACK Version 3.12.0 and SRC/checon_3.f(3) — source/version info, and no date is printed on this one, just so you know 🌈✨ byeeee 🫶