subroutine zla_lin_berr (N, NZ, NRHS, RES, AYB, BERR)
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.
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.
Univ. of Tennessee Univ. of California Berkeley Univ. of Colorado Denver NAG Ltd.Date:
September 2012Definition at line 102 of file zla_lin_berr.f.