Gurobi SOS constraint object. SOS constraints are always associated with a particular model. You create an SOS object by adding an SOS constraint to a model (using GRBModel.AddSOS), rather than by using a GRBSOS constructor. Similarly, SOS constraints are removed using the GRBModel.Remove method.

An SOS constraint can be of type 1 or 2 (GRB.SOS_TYPE1 or GRB.SOS_TYPE2). A type 1 SOS constraint is a set of variables for which at most one variable in the set may take a value other than zero. A type 2 SOS constraint is an ordered set of variables where at most two variables in the set may take non-zero values. If two take non-zero values, they must be contiguous in the ordered set.

SOS constraint objects have one attribute, IISSOS, which can be queried with the GRBSOS.Get method.