dla_lin_berr (3)

Functions/Subroutines

subroutine dla_lin_berr (N, NZ, NRHS, RES, AYB, BERR)

DLA_LIN_BERR computes a component-wise relative backward error.

subroutine dla_lin_berr (integerN, integerNZ, integerNRHS, 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.

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:

N

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

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.

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.

RES

          RES is DOUBLE PRECISION array, dimension (N,NRHS)
     The residual matrix, i.e., the matrix R in the relative backward
     error formula above.

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).

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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