Provided by: liblapack-doc_3.3.1-1_all

#### NAME

```       LAPACK-3  -  CLA_LIN_BERR  compute 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

```

#### SYNOPSIS

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

IMPLICIT            NONE

INTEGER             N, NZ, NRHS

REAL                AYB( N, NRHS ), BERR( NRHS )

COMPLEX             RES( N, NRHS )

```

#### PURPOSE

```          CLA_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.
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 cla_gerfsx_extended.f).

BERR   (output) COMPLEX array, dimension (NRHS)
The componentwise relative backward error from the formula above.

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