This commit adds sequential solvers, including a simulator variant
using them (flow_sequential.cpp) with an integration test (running
SPE1, same as for fully implicit).
The sequential code is capable of running several (but not all) test
cases without tuning or special parameters, but reducing ds_max a bit
(from default 0.2 to say 0.1) helps with transport solver
convergence. The Norne model runs fine (esp. with a little tuning). A
parameter iterate_to_fully_implicit (defaults to false) is available,
when set the simulator will iterate with alternating pressure and
transport solves towards the fully implicit solution. Although that
takes a lot extra time it serves as a correctness check.
Performance is not competitive with fully implicit at this point:
essentially both the pressure and transport models inherit the fully
implicit model and do a lot of double (or triple) work. The point has
been to establish a proof of concept and baseline for further
experiments, without disturbing the base model too much (or at all, if
possible).
Changes to existing code has been minimized by merging most such
changes as smaller PRs already, the only remaining such change is to
NewtonIterationBlackoilInterleaved. Admittedly, that code (to solve
the pressure system with AMG) is not ideal because it duplicates
similar code in CPRPreconditioner.hpp and is not parallel. I propose
to address this later by refactoring the "solve elliptic system" code
from CPRPreconditioner into a separate class that can be used also
from here
- For some cases (for instance involving solvent flow) the reasoning for
only adding the pressure derivatives seems to fail. As getting the
sparsity pattern is non-trivial, in terms of work, the full sparsity
pattern is only added when specified by the parameter
"require_full_sparsity_pattern"
- For solvent runs "require_full_sparsity_pattern" defaults to true for
all other runs the default is to only extract the sparsity pattern from
the pressure derivatives.
the Iteration for a fixed number of cell variabled which is then used by the
NewtonBlackølInterationInterleaved class via a switch-case over the actually existing
numbers.
The last parameter of this functions specifies how vector/martix
entries there are per index/cell of the grid. For the interleaved
versions all components end up in one block. Therefore this number
needs to be one here (in contrast to the number of phases for the
non-interleaved version).
This commit new uses the correct number.
The current implementation avoids the using of formEllipticSystem() and
vercatCollapseJacs(), which take a significant amount of computing time
during the non-linear solutions.
