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LAPACK
3.7.0
LAPACK: Linear Algebra PACKage
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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 component-wise relative backward error.
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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.
[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. |
Definition at line 103 of file dla_lin_berr.f.