1. A processing system capable of performing concurrent graphics computation, comprising: a plurality of computation elements, each computation element comprising a local memory, and a plurality of Single Instruction Multiple Data (SIMD) Arithmetic Logic Units (ALUs); a scheduler for the cluster of computation elements, the scheduler operable to receive inputs defining instances of a first type of computation to be performed on the cluster, each of the instances associated with a respective scheduling key, the scheduler operable to sort the instances according to their scheduling keys into packets, and emit a packet comprising a plurality of instances of computation; and a distributor operable to receive the packet, and distribute the instances among the computation elements of the cluster, for execution thereon, wherein each of the computation elements is operable to combine instances with different scheduling keys for concurrent execution, for which the same computation is to be performed and to concurrently execute the computation for the combined instances of computation.