dla_lin_berr.f(3)

NAME
dla_lin_berr.f -

SYNOPSIS

  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 (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.

Author

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