LAPACK
3.4.2
LAPACK: Linear Algebra PACKage

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Functions/Subroutines  
subroutine  dla_lin_berr (N, NZ, NRHS, RES, AYB, BERR) 
DLA_LIN_BERR computes a componentwise relative backward error. 
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 computes a componentwise relative backward error.
Download DLA_LIN_BERR + dependencies [TGZ] [ZIP] [TXT]DLA_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.
[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 componentwise relative backward error from the formula above. 
Definition at line 102 of file dla_lin_berr.f.