nag_superlu_diagnostic_lu (f11mmc) computes the reciprocal pivot growth factor of an factorization of a real sparse matrix in compressed column (Harwell–Boeing) format.
nag_superlu_diagnostic_lu (f11mmc) computes the reciprocal pivot growth factor
from the columns
and
of an
factorization of the matrix
,
where
is a row permutation matrix,
is a column permutation matrix,
is unit lower triangular and
is upper triangular as computed by
nag_superlu_lu_factorize (f11mec).
None.
Not applicable.
Not applicable.
If the reciprocal pivot growth factor,
rpg, is much less than
, then the factorization of the matrix
could be poor. This means that using the factorization to obtain solutions to a linear system, forward error bounds and estimates of the condition number could be unreliable. Consider increasing the
thresh argument in the call to
nag_superlu_lu_factorize (f11mec).
To compute the reciprocal pivot growth for the factorization of the matrix
, where
In this case, it should be equal to
.