1. A computer program product for processing a stream of tuples, the computer program product comprising a computer readable storage medium having program code embodied therewith, the program code comprising computer readable program code configured to: receive a stream of tuples to be processed by a plurality of processing elements operating on one or more computer processors, each processing element having one or more stream operators; identifying a grouping location within the plurality of stream operators to modify processing the stream of tuples during runtime; and modifying processing at a first stream operator within a processing location, the modifying including adding a runtime grouping condition to the first stream operator such that the first stream operator groups a plurality of tuples to send to a second stream operator.