LAPACK  3.4.1
LAPACK: Linear Algebra PACKage
dla_lin_berr.f File Reference

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Functions/Subroutines

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

Function/Subroutine Documentation

subroutine DLA_LIN_BERR ( INTEGER  N,
INTEGER  NZ,
INTEGER  NRHS,
DOUBLE PRECISION, dimension( n, nrhs )  RES,
DOUBLE PRECISION, dimension( n, nrhs )  AYB,
DOUBLE PRECISION, dimension( nrhs )  BERR 
)

DLA_LIN_BERR

Download DLA_LIN_BERR + dependencies [TGZ] [ZIP] [TXT]
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.
 
Parameters:
[in]N
          N is INTEGER
     The number of linear equations, i.e., the order of the
     matrix A.  N >= 0.
 
[in]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.
 
[in]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.
 
[in]RES
          RES is DOUBLE PRECISION array, dimension (N,NRHS)
     The residual matrix, i.e., the matrix R in the relative backward
     error formula above.
 
[in]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 dla_gerfsx_extended.f).
 
[out]BERR
          BERR is DOUBLE PRECISION array, dimension (NRHS)
     The component-wise relative backward error from the formula above.
 
Author:
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
November 2011

Definition at line 102 of file dla_lin_berr.f.

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