# sla_lin_berr.f - Man Page

SRC/sla_lin_berr.f

## Synopsis

### Functions/Subroutines

subroutine sla_lin_berr (n, nz, nrhs, res, ayb, berr)
SLA_LIN_BERR computes a component-wise relative backward error.

## Function/Subroutine Documentation

### subroutine sla_lin_berr (integer n, integer nz, integer nrhs, real, dimension( n, nrhs ) res, real, dimension( n, nrhs ) ayb, real, dimension( nrhs ) berr)

SLA_LIN_BERR computes a component-wise relative backward error.

Purpose:

```    SLA_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.```
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 REAL array, dimension (N,NRHS)
The residual matrix, i.e., the matrix R in the relative backward
error formula above.```

AYB

```          AYB is REAL 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 sla_gerfsx_extended.f).```

BERR

```          BERR is REAL array, dimension (NRHS)
The componentwise relative backward error from the formula above.```
Author

Univ. of Tennessee

Univ. of California Berkeley

NAG Ltd.

Definition at line 100 of file sla_lin_berr.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

The man page sla_lin_berr(3) is an alias of sla_lin_berr.f(3).

Tue Nov 28 2023 12:08:42 Version 3.12.0 LAPACK