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zla_lin_berr.f(3) LAPACK zla_lin_berr.f(3)

zla_lin_berr.f -


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

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.
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 zla_gerfsx_extended.f).
BERR
          BERR is COMPLEX*16 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 zla_lin_berr.f.

Generated automatically by Doxygen for LAPACK from the source code.
Sat Nov 16 2013 Version 3.4.2

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