zla_lin_berr()

subroutine zla_lin_berr	(	integer	n,
		integer	nz,
		integer	nrhs,
		complex*16, dimension( n, nrhs )	res,
		double precision, dimension( n, nrhs )	ayb,
		double precision, dimension( nrhs )	berr )

ZLA_LIN_BERR computes a component-wise relative backward error.

Download ZLA_LIN_BERR + dependencies [TGZ] [ZIP] [TXT]

Purpose:

!>
!>    ZLA_LIN_BERR computes componentwise relative backward error from
!>    the formula
!>        max(i) ( abs(R(i)) / ( abs(op(A_s))*abs(Y) + abs(B_s) )(i) )
!>    where abs(Z) is the componentwise absolute value of the matrix
!>    or vector Z.
!> 

Parameters

[in]	N	!> N is INTEGER !> The number of linear equations, i.e., the order of the !> matrix A. N >= 0. !>
[in]	NZ	!> NZ is INTEGER !> We add (NZ+1)*SLAMCH( 'Safe minimum' ) to R(i) in the numerator to !> guard against spuriously zero residuals. Default value is N. !>
[in]	NRHS	!> NRHS is INTEGER !> The number of right hand sides, i.e., the number of columns !> of the matrices AYB, RES, and BERR. NRHS >= 0. !>
[in]	RES	!> RES is COMPLEX*16 array, dimension (N,NRHS) !> The residual matrix, i.e., the matrix R in the relative backward !> error formula above. !>
[in]	AYB	!> AYB is DOUBLE PRECISION array, dimension (N, NRHS) !> The denominator in the relative backward error formula above, i.e., !> the matrix abs(op(A_s))*abs(Y) + abs(B_s). The matrices A, Y, and B !> are from iterative refinement (see zla_gerfsx_extended.f). !>
[out]	BERR	!> BERR is DOUBLE PRECISION array, dimension (NRHS) !> The componentwise relative backward error from the formula above. !>

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.