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zla_lin_berr.f -

# SYNOPSIS

## Functions/Subroutines

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

ZLA_LIN_BERR computes a component-wise relative backward error.

# Function/Subroutine Documentation

## subroutine zla_lin_berr (integerN, integerNZ, integerNRHS, complex*16, dimension( n, nrhs )RES, double precision, dimension( n, nrhs )AYB, double precision, dimension( nrhs )BERR)

ZLA_LIN_BERR computes a component-wise relative backward error.
Purpose:
```    ZLA_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 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 zla_gerfsx_extended.f).
```
BERR
```          BERR is COMPLEX*16 array, dimension (NRHS)
The componentwise relative backward error from the formula above.
```
Author:
Univ. of Tennessee
Univ. of California Berkeley
NAG Ltd.
Date:
September 2012
Definition at line 102 of file zla_lin_berr.f.

# Author

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