A data processing system includes a set of architected registers within which the processor places state and other information to communicate with the asynchronous memory mover in order to initiate and control an AMM operation. During operation, the system obtains information on a number of principals and constructs one or more first-level groups of principals. Each clip element has a gripping element opposite the tines. One or more courses of blocks can be vertically stacked over the base track by passing the T-shaped reinforcement members andor extension members through the apertures formed in the blocks, thereby forming the wall structure. The thickness of each of the lenses constituting the lens array is adjusted such that the step difference at the boundaries between the lenses falls within a predetermined step difference.