SRC/dla_porpvgrw.f(3)

okay bestie, welcome to SRC/dla_porpvgrw.f(3) from the Library Functions Manual — this is the double precision reciprocal-pivot-growth-factor girlie, and it’s lowkey iconic 🦋✨.

NAME 💅

SRC/dla_porpvgrw.f — that’s it, that’s the name, no cap.

SYNOPSIS 🌸

Functions/Subroutines

double precision function dla_porpvgrw (uplo, ncols, a, lda, af, ldaf,
    work)

DLA_PORPVGRW computes the reciprocal pivot growth factor norm(A)/norm(U) for a symmetric or Hermitian positive-definite matrix.

Function/Subroutine Documentation ✨

double precision function dla_porpvgrw (character*1 uplo, integer ncols,
    double precision, dimension( lda, * ) a, integer lda, double precision,
    dimension( ldaf, * ) af, integer ldaf, double precision, dimension( * )
    work)

DLA_PORPVGRW computes the reciprocal pivot growth factor norm(A)/norm(U) for a symmetric or Hermitian positive-definite matrix.

Purpose 🎯

So the purpose is giving: DLA_PORPVGRW computes the reciprocal pivot growth factor norm(A)/norm(U). The norm is used. If this is much less than 1, the stability of the LU factorization of the (equilibrated) matrix A could be poor. This also means that the solution X, estimated condition numbers, and error bounds could be unreliable. (In the source, these lines are wrapped in !> Doxygen comment markers, iykyk.)

Parameters 🌸

• UPLO — CHARACTER*1. = 'U': upper triangle of A is stored; = 'L': lower triangle of A is stored.
• NCOLS — INTEGER. The number of columns of the matrix A. NCOLS >= 0.
• A — DOUBLE PRECISION array, dimension (LDA,N). On entry, the N-by-N matrix A.
• LDA — INTEGER. The leading dimension of the array A. LDA >= max(1,N).
• AF — DOUBLE PRECISION array, dimension (LDAF,N). The triangular factor U or L from the Cholesky factorization A = U**T*U or A = L*L**T, as computed by DPOTRF.
• LDAF — INTEGER. The leading dimension of the array AF. LDAF >= max(1,N).
• WORK — DOUBLE PRECISION array, dimension (2*N).

Author 👑

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

Definition at line 104 of file dla_porpvgrw.f.

Author (auto-generated edition) 💖

Generated automatically by Doxygen for LAPACK from the source code.

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