dla_lin_berr.f File Reference

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Functions/Subroutines
subroutine	dla_lin_berr (N, NZ, NRHS, RES, AYB, BERR)
	DLA_LIN_BERR computes a component-wise relative backward error.

---

Function/Subroutine Documentation

subroutine dla_lin_berr	(	integer	N,
		integer	NZ,
		integer	NRHS,
		double precision, dimension( n, nrhs )	RES,
		double precision, dimension( n, nrhs )	AYB,
		double precision, dimension( nrhs )	BERR
	)

DLA_LIN_BERR computes a component-wise relative backward error.

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Purpose:

    DLA_LIN_BERR computes component-wise 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 component-wise 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 DOUBLE PRECISION 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 dla_gerfsx_extended.f).
[out]	BERR	BERR is DOUBLE PRECISION array, dimension (NRHS) The component-wise relative backward error from the formula above.

Author:

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Date:

September 2012

Definition at line 102 of file dla_lin_berr.f.

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