Add lazy constraints at runtime

[lmores]

Hi everyone, I would like to try out and experiment with SCIP using the Java API. However, it is unclear to me whether the Java API allows to add user defined cuts and/or lazy constraints while SCIP is solving a model.

E.g.: could I solve a simple Travelling Salesmann Problem starting from an incomplete model with just "flow constraints" and add Subtour Elimination Constraints and/or Connectivity Constraints manually at runtime?

Thank you a lot!

[kkofler]

At this time, no. But it can be added, though I do not have the time to do so myself at the moment.

How you would go at it is:

1. figure out the C APIs that you need (or if, as for the constraint handlers, they involve callbacks, the C++ objscip wrappers with the callback classes),
2. add them to scipjni.i (for the callback classes, see how I did it for ObjMessagehdlr),
3. add them to the object-oriented Java wrapper classes in the java/jscip folder, and
4. when done, submit a pull request to this repository (thereby acknowledging and authorizing that the code will be released under the MIT License as shipped in the LICENSE file).

[lmores]

Thanks a lot for the hints. Being the very first time time I am using SCIP I hoped I could use Java to avoid the complexity of C and C++ that requires manual memory management and longer implementation times. If I find some spare time I will try my best and (if I succeed) I will open a PR.

[kkofler]

The good thing about JSCIP is that the hard part of doing the C/C++ to Java binding is done by the SWIG binding generator.