Forum Discussion
Lazy cut callback in Java
In Java, how can one separate cuts in a lazy manner, i.e. only separate cuts at the integer nodes? Such an approach is common in for instance a standard TSP formulation where the subtour elimination ...
Hi Joris, sorry for the long delay. I first had a hard time reproducing your issue and then got side-tracked by some other things.
Here is what I found by now:
We get into an infinite loop because the example separates the same cut over and over again. This happens for two reasons
- The example separates cuts even for nodes that are not integer feasible.
- The example does not check whether the cut is sufficiently violated before adding it
I suggest to separate cuts only for integer feasible nodes (prob.attributes().getMIPInfeas() == 0) that should fix both issues (because any violated cut found that way will be significantly violated). It also reduces the overhead for non-integral nodes.
An alternative is of course to check that the presolved cut is sufficiently violated. For this you will need the solution to the presolved problem. That can be obtained by function prob.getPresolveSol().