System, method, and program for optimally caching overlay instances in a memory system

A system, method, and program for optimally caching in a memory system an overlay instance. The system includes a local memory and a rasterizing processor coupled to the local memory. Responsive to receipt of a presentation requirement specifying an overlay stored in a memory device, the rasterizing processor determines whether an overlay instance for the overlay is cached in a memory system. Responsive to the overlay instance not being cached in the memory system, the rasterizing processor generates a new overlay instance for the overlay and caches the new overlay instance in the memory system. Responsive to the overlay instance being cached in the memory system, the rasterizing processor produces another overlay instance tailored to the presentation requirements, compares the another overlay instance to the cached overlay instance and then caches into the memory system only one overlay instance among the another overlay instance and the cached overlay instance that best presents the overlay. The rasterizing processor discards the other overlay instance.