dla_gbrpvgrw.f

Section: LAPACK (3)
Updated: Tue Nov 14 2017
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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 (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.


 

Index

NAME
SYNOPSIS
Functions/Subroutines
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)
Author