We introduced two runtime parameters for this: ilu_redblack and
ilu_reorder_spheres. If the last one is false, we try to preserve
the ordering within in the colors. Otherwise we try to achieve a D2
(alternative diagonal) ordering.
These versions are inspired by the ones used in SuperLU and the enums
to choose them have simuilar names, but without leading S (MILU_1-MILU_3).
The following variants are supported (chosen by the enum MILU_VARIANT):
ILU: plain ILU
MILU_1: lump diagonal with dropped row entries.
MILU_2: lump diagonal with the sum of the absolute values of the dropped row
entries.
MILU_3: if diagonal is positive add sum of dropped row entrires. Otherwise substract them.
MILU_4: if diagonal is positive add sum of dropped row entrires. Otherwise do nothing
These versions are inspired by the ones used in SuperLU and the enums
to choose them have simuilar names, but without leading S (MILU_1-MILU_3).
The following variants are supported (chosen by the enum MILU_VARIANT):
ILU: plain ILU
MILU_1: lump diagonal with dropped row entries.
MILU_2: lump diagonal with the sum of the absolute values of the dropped row
entries.
MILU_3: if diagonal is positive add sum of dropped row entrires. Otherwise substract them.
MILU_4: if diagonal is positive add sum of dropped row entrires. Otherwise do nothing
We did add the dropped matrix blocks to the diagonal blocks,
but this is not MILU where oone only modifies the diagonal.
With this patch we fix this behaviour and now only modify the
diagonal of the diagonal block.
Using the parameter ilu_milu=true|false (default=false) the user can now choose
to use the modified ILU0 decomposition. If selected values will
not be dropped for nonzero entries but added to the diagonal of U.
This approach will result in A*e = L*U*e for vector e with all entries
beging 1.
this is necessiated by the replacement of `std::shared_ptr` by raw
pointers for the eWoms auxiliary equation infrastructure. Note that by
default `flow` will *not* create an auxiliary equation module because
it modifies the operator that is used by the linear solver instead.
