A data processing unit, a data processing method, and a program product for determining a transhipment method are provided. The data processing unit may include a solution search processor for performing solution search processing of a plurality of physical objects. In the data processing unit, a data representation of a loading state of an object may have a corresponding variable which takes as a value an identification number of a heap at a predetermined physical location. The data representation of the loading state may include a coordinate value indicating a loading order of the object in the heap. The data processing unit may also include an initial condition inputter. The solution search processor may perform the solution search processing by constructing a search tree.