 LAPACK  3.4.2 LAPACK: Linear Algebra PACKage
sla_lin_berr.f File Reference

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## 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.

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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:
 [in] N ``` N is INTEGER The number of linear equations, i.e., the order of the matrix A. N >= 0.``` [in] 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.``` [in] 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.``` [in] RES ``` RES is REAL array, dimension (N,NRHS) The residual matrix, i.e., the matrix R in the relative backward error formula above.``` [in] 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).``` [out] BERR ``` BERR is REAL array, dimension (NRHS) The componentwise relative backward error from the formula above.```
Date:
September 2012

Definition at line 102 of file sla_lin_berr.f.

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