OPTIMIZE CONTROL-FLOW CONVERGENCE ON SIMD ENGINE USING DIVERGENCE DEPTH

There are provided a system, a method and a computer program product for selecting an active data stream (a lane) while running SPMD (Single Program Multiple Data) code on SIMD (Single Instruction Multiple Data) machine. The machine runs an instruction stream over input data streams. The machine increments lane depth counters of all active lanes upon the thread-PC reaching a branch operation. The machine updates the lane-PC of each active lane according to targets of the branch operation. The machine selects an active lane and activates only lanes whose lane-PCs match the thread-PC. The machine decrements the lane depth counters of the selected active lanes and updates the lane-PC of each active lane upon the instruction stream reaching a first instruction. The machine assigns the lane-PC of a lane with a largest lane depth counter value to the thread-PC and activates all lanes whose lane-PCs match the thread-PC.