external force density in first integration step

[KaiSzuttor]

Fixes #2875

Description of changes:

• initialize the force density member with the external force density set by the user
• if node velocity is set from the interface, the force density on this node is reset

[codecov]

Codecov Report

Merging #3144 into python will increase coverage by <1%.
The diff coverage is 100%.

@@           Coverage Diff            @@
##           python   #3144     +/-   ##
========================================
+ Coverage      84%     84%    +<1%     
========================================
  Files         526     523      -3     
  Lines       26091   24881   -1210     
========================================
- Hits        22138   21142    -996     
+ Misses       3953    3739    -214

Impacted Files	Coverage Δ
src/core/grid_based_algorithms/lbgpu.hpp	100% <ø> (ø)	⬆️
src/core/grid_based_algorithms/lb.hpp	100% <ø> (ø)	⬆️
src/core/grid_based_algorithms/lb_interface.cpp	72% <100%> (-4%)	⬇️
src/core/grid_based_algorithms/lb.cpp	96% <100%> (-1%)	⬇️
...ore/grid_based_algorithms/lb_particle_coupling.cpp	86% <0%> (-12%)	⬇️
src/core/specfunc.cpp	72% <0%> (-9%)	⬇️
src/core/rotation.cpp	91% <0%> (-7%)	⬇️
src/core/RuntimeErrorStream.cpp	60% <0%> (-4%)	⬇️
...ipt_interface/constraints/ShapeBasedConstraint.hpp	90% <0%> (-4%)	⬇️
... and 155 more

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[KaiSzuttor]

ready for review @RudolfWeeber

[RudolfWeeber]

The call

    lbfields = lb_get_initialized_fields(lbpar, lblattice);

might result in the fields array to be allocated twice (once the previous value of fields, once the one instanced in the funciton.).
Probably better pass fields as a reference to the funciton.
Also, please add doxgen for teh funciotn since it has some non-obvious logic.

There is a lot of unrelated formatting in there. Please check that your autopep8 args and version match the one in the CI.

[KaiSzuttor]

sorry, I forgot to enable some formatting flags... the version is the same as in the CI

[RudolfWeeber]

bors r+

[bors]

Build succeeded

• ICP GitLab CI