Provided by: liblapack-doc_3.3.1-1_all bug

NAME

       LAPACK-3  -  DLA_LIN_BERR compute component-wise 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
       component-wise absolute value of the matrix  or vector Z

SYNOPSIS

       SUBROUTINE DLA_LIN_BERR ( N, NZ, NRHS, RES, AYB, BERR )

           IMPLICIT            NONE

           INTEGER             N, NZ, NRHS

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

           DOUBLE              PRECISION RES( N, NRHS )

PURPOSE

          DLA_LIN_BERR computes component-wise 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 component-wise absolute value of the matrix
          or vector Z.

ARGUMENTS

        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 dla_gerfsx_extended.f).
                 BERR    (output) DOUBLE PRECISION array, dimension (NRHS)
                The component-wise relative backward error from the formula above.

    LAPACK routine (version 3.2.2)          April 2011                      DLA_LIN_BERR(3lapack)