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dla_gbrpvgrw.f(3) LAPACK dla_gbrpvgrw.f(3)

NAME

dla_gbrpvgrw.f -

SYNOPSIS

Functions/Subroutines


DOUBLE PRECISION function dla_gbrpvgrw (N, KL, KU, NCOLS, AB, LDAB, AFB, LDAFB)
DLA_GBRPVGRW computes the reciprocal pivot growth factor norm(A)/norm(U) for a general banded matrix.

Function/Subroutine Documentation

DOUBLE PRECISION function dla_gbrpvgrw (integerN, integerKL, integerKU, integerNCOLS, double precision, dimension( ldab, * )AB, integerLDAB, double precision, dimension( ldafb, * )AFB, integerLDAFB)

DLA_GBRPVGRW computes the reciprocal pivot growth factor norm(A)/norm(U) for a general banded matrix.

Purpose:


DLA_GBRPVGRW computes the reciprocal pivot growth factor
norm(A)/norm(U). The "max absolute element" 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.

Parameters:

N


N is INTEGER
The number of linear equations, i.e., the order of the
matrix A. N >= 0.

KL


KL is INTEGER
The number of subdiagonals within the band of A. KL >= 0.

KU


KU is INTEGER
The number of superdiagonals within the band of A. KU >= 0.

NCOLS


NCOLS is INTEGER
The number of columns of the matrix A. NCOLS >= 0.

AB


AB is DOUBLE PRECISION array, dimension (LDAB,N)
On entry, the matrix A in band storage, in rows 1 to KL+KU+1.
The j-th column of A is stored in the j-th column of the
array AB as follows:
AB(KU+1+i-j,j) = A(i,j) for max(1,j-KU)<=i<=min(N,j+kl)

LDAB


LDAB is INTEGER
The leading dimension of the array AB. LDAB >= KL+KU+1.

AFB


AFB is DOUBLE PRECISION array, dimension (LDAFB,N)
Details of the LU factorization of the band matrix A, as
computed by DGBTRF. U is stored as an upper triangular
band matrix with KL+KU superdiagonals in rows 1 to KL+KU+1,
and the multipliers used during the factorization are stored
in rows KL+KU+2 to 2*KL+KU+1.

LDAFB


LDAFB is INTEGER
The leading dimension of the array AFB. LDAFB >= 2*KL+KU+1.

Author:

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Date:

September 2012

Definition at line 117 of file dla_gbrpvgrw.f.

Author

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Tue Sep 25 2012 Version 3.4.2