Provided by: liblapack-doc_3.3.1-1_all

#### NAME

```       LAPACK-3  -  DLA_LIN_BERR compute 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

```

#### SYNOPSIS

```       SUBROUTINE DLA_LIN_BERR ( N, NZ, NRHS, RES, AYB, BERR )

IMPLICIT            NONE

INTEGER             N, NZ, NRHS

DOUBLE              PRECISION AYB( N, NRHS ), BERR( NRHS )

DOUBLE              PRECISION RES( N, NRHS )

```

#### 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.

```

#### ARGUMENTS

```        N       (input) INTEGER
The number of linear equations, i.e., the order of the
matrix A.  N >= 0.

NZ      (input) 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    (input) INTEGER
The number of right hand sides, i.e., the number of columns
of the matrices AYB, RES, and BERR.  NRHS >= 0.

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

AYB     (input) 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    (output) DOUBLE PRECISION array, dimension (NRHS)
The component-wise relative backward error from the formula above.

LAPACK routine (version 3.2.2)          April 2011                      DLA_LIN_BERR(3lapack)
```