The class ABA_MASTER augments the data inherited from the class ABA_GLOBAL with specific data members and functions for branch-and-bound. It has objects of classes as members that store the list of subproblems which still have to be processed in the implicit enumeration (class ABA_OPENSUB ), and that store the variables which might be fixed by reduced cost criteria in later iterations (class ABA_FIXCAND ). Moreover, the solution history, timers for parts of the optimization, and a lot of other statistical information is stored within the class ABA_MASTER.
The class ABA_MASTER also provides default implementations of pools for
the storage of constraints and variables. We explain the details in
Section 
.
A branch-and-bound framework requires also a flexible way for defining enumeration
strategies. The corresponding virtual functions are defined in the
class ABA_MASTER, but for a better understanding we explain this concept
in Section ,
when we discuss the data structure for the open subproblems.