| 主权项 |
1. A method for selecting an active data stream while running a SPMD (Single Program Multiple Data) program of instructions on a SIMD (Single Instruction Multiple Data) machine, an instruction stream having one thread-PC (Program Counter), the thread-PC indicating an instruction memory address which stores an instruction to be fetched next for the instruction stream;
running the instruction stream over one or more input data streams (“lanes”), each lane being associated with a corresponding lane depth counter, a corresponding lane-PC of a lane indicating a memory address which stores the instruction to be fetched next for the lane when the lane is activated, and a lane activation bit indicating whether a corresponding lane is active or not; incrementing lane depth counters of all active lanes upon the thread-PC reaching a branch operation in the instruction stream; updating the lane-PC of each active lane according to targets of the branch operation; and selecting one or more active lanes and assigning a corresponding lane-PC to the thread-PC, and activating only lanes whose lane-PC matches the thread-PC; decrementing the lane depth counters of the selected active lanes and updating the lane-PC of each active lane upon the instruction stream reaching a first instruction; and assigning the lane-PC of a lane with a largest lane depth counter value to the thread-PC and activating all lanes whose lane-PCs match the thread-PC, wherein a plurality of processors coupled to one or more memory devices perform the running, the incrementing, the assigning, the activating and the decrementing until the thread-PC reaches an end of the instruction stream and the lane-PCs of all lanes match with the thread-PC. |
