[SCIP] Duplicate rows in branch-and-cut-and-price

[Edward Lam]

Hi all,

I have a constraint handler that is adding setppc constraints (not rows/cuts) in the enfolp callback. I expect the setppc constraint to then add a row into the LP. It appears that sometimes this row is not in the LP (or removed) so my separator is adding a duplicate setppc constraint.

This also occurs when I tried separating rows directly. Sometimes they are not in the LP, so I’m separating the same rows again.

Why does this occur? Is there a way to tell SCIP to simply add the existing row back into the LP?

Also, is there any benefit to separating constraints vs. rows? I assume constraints will improve primal heuristics and propagation. Although I’m not sure what can be propagated in column generation since setting a variable to 0 will regenerate that column and setting it to 1 will prevent future better columns from generating.

Thanks in advance.

Cheers
Eddie
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