subroutine cla_lin_berr (N, NZ, NRHS, RES, AYB, BERR)
CLA_LIN_BERR computes a component-wise relative backward error.
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 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 COMPLEX 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 cla_gerfsx_extended.f).
BERR
BERR is REAL array, dimension (NRHS) The componentwise relative backward error from the formula above.
Author:
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
Definition at line 103 of file cla_lin_berr.f.
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