so far, the linker bailed out due to duplicate definitions of
variables if multiple compile units used the same type tag. This is
problematic if the sources are split into separate compile units and
that use the same type tag; in particular, this applies for
traditional libraries.
Due to various C++ peculiarities, this patch complicates the internal
implementation of the property system quite a bit, but given that the
usage of it (as well as the compile time) stay unchanged, I do not
consider this to be a big problem. Note that the introspection code is
particularly problematic because it needs static initializers that do
not cause the linker to choke in the case of multiple compile units.
Finally, to prevent future regressions, this patch adds a unit test
for the lens problem which uses multiple compile units. (This test is
called lens_immiscible_ecfv_ad_mcu and basically identical to the
existing lens_immiscible_ecfv_ad test and I thus think that it is
pretty unimaginative -- improvement proposals are welcome.)
This works by having a "focus degree of freedom" during
linearization. When evaluating the local residual, all derivatives of
the residual/fluxes are with regard to the primary variables of that
DOF.
The two main offenders were the Forchheimer velocity model and the
model for the Stokes equations. To ensure that they continue to work,
the "powerinjection" and the "stokestest2c" problems are now both
compiled and tested with both, automatic differentiation and finite
differences, and the results of these tests is compared against the
same reference solution.
The majority of the time required to develop this patch was actually
required for testing: All tests compile and pass with debugging and
aggressive optimization flags with at least GCC 5, GCC 7 and clang
3.8, as well as Dune 2.3 and 2.4. Also, the results of flow_ebos stay
identical for Norne whilst the performance difference is below the
measurement noise on my machine. (the version with this patch applied
was actually about 1% faster.)
