Developer Reference for Intel® oneAPI Math Kernel Library for Fortran
?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.