cla_lin_berr-f(3)

cla_lin_berr.f –

Synopsis

Functions/Subroutines

subroutine cla_lin_berr (N, NZ, NRHS, RES, AYB, BERR)
CLA_LIN_BERR computes a component-wise relative backward error.

Function/Subroutine Documentation

subroutine cla_lin_berr (integerN, integerNZ, integerNRHS, complex, dimension( n, nrhs )RES, real, dimension( n, nrhs )AYB, real, dimension( nrhs )BERR)

CLA_LIN_BERR computes a component-wise relative backward error.

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.

 

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 cla_gerfsx_extended.f).

BERR

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

 

Author:

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Date:

September 2012

Definition at line 102 of file cla_lin_berr.f.

Author

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