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LAPACK-3

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LAPACK-3: ZLA_LIN_BERR compute componentwise relative backward error from the formula max(i) ( abs(R(i)) / ( abs(op(A_s))*abs(Y)

NAME
       LAPACK-3  -  ZLA_LIN_BERR compute 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

SYNOPSIS
       SUBROUTINE ZLA_LIN_BERR ( N, NZ, NRHS, RES, AYB, BERR )

           IMPLICIT            NONE

           INTEGER             N, NZ, NRHS

           DOUBLE              PRECISION AYB( N, NRHS ), BERR( NRHS )

           COMPLEX*16          RES( N, NRHS )

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       (input) INTEGER
           The number of linear equations, i.e., the order of the
           matrix A.  N >= 0.
           NZ      (input) 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    (input) INTEGER
           The number of right hand sides, i.e., the number of columns
           of the matrices AYB, RES, and BERR.  NRHS >= 0.
           RES    (input) DOUBLE PRECISION array, dimension (N,NRHS)
           The residual matrix, i.e., the matrix R in the relative backward
           error formula above.
           AYB    (input) 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   (output) COMPLEX*16 array, dimension (NRHS)
           The componentwise relative backward error from the formula above.

    LAPACK routine (version 3.2.2)March 2011                       LAPACK-3(3)