Originally posted by: VKV7_Anulark_Naber

Is there any relationship between getFeasibility(binVar) and a variable eliminated by PreSolve? What I understand is that a binary variable that attains an integer value (o or 1), regardless of whether (1) it is fixed by branching, (2) its value in a relaxed solution is integer, or (3) it is fixed by PreSolve, will be "Feasible" by using getFeasibility(). For (1), I store the fixed values in nodedata. However, I cannot distinguish (2) from (3). Without knowing all fixed variables at that node, my cuts will not be tight.

1. How can I get the information of which variables are eliminated or fixed by PreSolve, using C++ API? I saw in other thread that I won't be able to get this information except from the callable library. Is there any other way around it?

2. Can I presume that all "Feasible" variables will remain integers at their current values in the subsequent (children, grand..., etc.) nodes?

Thanks in advance.

1. getFeasibility() returns a value from the IntegerFeasibility enumeration and the reference documentation for that enumeration specifies that variables that were presolved out have a value of ImpliedFeasible.

2. Of course you can not assume that. That a variable is integer in the solution to the current relaxation does not imply that it is integer in all relaxations in the subtree rooted at the current node.

Originally posted by: VKV7_Anulark_Naber

Great, that was what I missed. Thank you very much.