cla_lin_berr (3)  Linux Manuals
NAME
cla_lin_berr.f 
SYNOPSIS
Functions/Subroutines
subroutine cla_lin_berr (N, NZ, NRHS, RES, AYB, BERR)
CLA_LIN_BERR computes a componentwise 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 componentwise 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.
NZNZ 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.
NRHSNRHS is INTEGER The number of right hand sides, i.e., the number of columns of the matrices AYB, RES, and BERR. NRHS >= 0.
RESRES is REAL array, dimension (N,NRHS) The residual matrix, i.e., the matrix R in the relative backward error formula above.
AYBAYB 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 cla_gerfsx_extended.f).
BERRBERR 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:
 November 2013
Definition at line 102 of file cla_lin_berr.f.
Author
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