# dla_gbrpvgrw.f man page

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 (integer N, integer KL, integer KU, integer NCOLS, double precision, dimension( ldab, * ) AB, integer LDAB, double precision, dimension( ldafb, * ) AFB, integer LDAFB)

**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:**December 2016

Definition at line 119 of file dla_gbrpvgrw.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

The man page dla_gbrpvgrw(3) is an alias of dla_gbrpvgrw.f(3).

Tue Nov 14 2017 Version 3.8.0 LAPACK