Visible to Intel only — GUID: GUID-DA43ED17-684C-405D-A1A6-A210B2B5A8EE
Visible to Intel only — GUID: GUID-DA43ED17-684C-405D-A1A6-A210B2B5A8EE
?la_lin_berr
Computes component-wise relative backward error.
Syntax
call sla_lin_berr(n, nz, nrhs, res, ayb, berr )
call dla_lin_berr(n, nz, nrhs, res, ayb, berr )
call cla_lin_berr(n, nz, nrhs, res, ayb, berr )
call zla_lin_berr(n, nz, nrhs, res, ayb, berr )
Include Files
- mkl.fi
Description
The ?la_lin_berr computes a 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 value of the matrix or vector Z.
Input Parameters
- n
-
INTEGER. The number of linear equations, the order of the matrix A; n≥ 0.
- nz
-
INTEGER. The parameter for guarding against spuriously zero residuals.
(nz+1)*slamch( 'Safe minimum' ) is added to R(i) in the numerator of the relative backward error formula. The default value is n.
- nrhs
-
INTEGER. Number of right-hand sides, the number of columns in the matrices AYB, RES, and BERR; nrhs≥ 0.
- res, ayb
-
REAL for sla_lin_berr, cla_lin_berr
DOUBLE PRECISION for dla_lin_berr, zla_lin_berr
Arrays, DIMENSION (n,nrhs).
res is the residual matrix, that is, the matrix R in the relative backward error formula.
ayb is the denominator of that formula, that is, the matrix abs(op(A_s))*abs(Y) + abs(B_s). The matrices A, Y, and B are from iterative refinement. See description of ?la_gerfsx_extended.
Output Parameters
- berr
-
REAL for sla_lin_berr
DOUBLE PRECISION for dla_lin_berr
COMPLEX for cla_lin_berr
DOUBLE COMPLEX for zla_lin_berr
The component-wise relative backward error.