Need guidance for a PR

[patrickguenther]

Hello everyone,

I'm currently working on a PR, to expose SCIP's event handlers via the java API. I'm making good progress and am currently working on an example for running the travelling sales man problem to illustrate event handler usage and testing my implementation.
I have some questions, however:

• What is the maximum java version, I should target? From existing code I'm guessing 1.7, but I hope I can at least use 1.8 🙏 ?
• What version of SWIG am I supposed to use? I used 4.4.x or whatever was the most recent version in my package repository, but I found files that had been generated by 4.0.2, so I compiled 4.0.2 manually and then I found files generated by 4.2.x. So I guess, I just use whatever I want and roll back file changes that only change the version number in the generated comments?
• The scip_exec callback is receiving a pointer argument of type SCIP_Event (see struct_event.h) which contains data relevant to the event being observed. I have no clue however how to access it's fields or how they are layed out in memory with the union. I'm thinking about mapping it's type to a fixed-length byte array first and checking out it's content in the java debugger. I have no clue if that would work. Is there a recommended approach?

[patrickguenther]

Opened PR #61

I must be doing something wrong, as my subtour elimination constraints are not working.
As can be seen from the final solution given by scip:

Both visible subtours should be eliminated from the solution by constraints

 subtourElimination_9_6_5_3_0_1: +1 t_edge_1_0 +1 t_edge_3_0 +1 t_edge_5_3 +1 t_edge_6_5 +1 t_edge_9_1
  +1 t_edge_9_6 <= +5
 subtourElimination_8_4_7_2: +1 t_edge_7_2 +1 t_edge_7_4 +1 t_edge_8_2 +1 t_edge_8_4 <= +3

see attached lp.txt file

tsp.ign.lp.txt

There must be some mechanism to mark a solution as infeasible from an event handler or is there a dedicated method for adding cuts?

[patrickguenther]

Alright, from the pyscipopt sources I can infer, that I should have implemented cons handlers instead.
But I can still leave my changes and attach also add cons handlers to this PR.

What would be a good example usage for those regular event handlers be?