layered: Added model order cycle breaker.

[soerendomroes]

Added a cycle breaker that reverses edges going against the model order.
Edges should always go from low model order to high model order.

• Using this strategy in a model with layer constraints causes an NPE. One could either ignore these layer constraints and only use the model order or use it additionally to the model order (which might be the better solution).
• Check whether hierarchical and normal graphs cover this cycle breaker via tests

Signed-off-by: Soeren Domroes sdo@informatik.uni-kiel.de

[soerendomroes]

@uruuru Any idea why elkjs is not working? Something seems to use Java 11 instead of Java 8.

[uruuru]

Using this strategy in a model with layer constraints causes an NPE. One could either ignore these layer constraints and only use the model order or use it additionally to the model order (which might be the better solution).

What happens if the constraints are added programatically, for instance, for hierarchical ports? What is the model index of a hierarchical port's dummy node in the first place? Did you check with hierarchical graphs?

Could you please also check if there are unit tests where you'd have to manually add this strategy? Or are existing tests succeeding?

[soerendomroes]

Somehow the ModelOrderCycleBreaker seems to create graphs that cannot be handled by the SortByInputModelOrderProcessor. Using only one of them does not cause problems.

Solved by handling saving the transitive dependencies and using them instead.

[soerendomroes]

What happens if the constraints are added programmatically, for instance, for hierarchical ports? What is the model index of a hierarchical port's dummy node in the first place? Did you check with hierarchical graphs?

Checked everything, programmatic constraints are handled now.

Could you please also check if there are unit tests where you'd have to manually add this strategy? Or are existing tests succeeding?

I added this cycle breaker to the BasicCycleBreakerTest