Abstract: Variable Instruction Issue for Efficient MIMD Interpretation on SIMD Machines.

Multiple execution threads can be simulated on Single Instruction Multiple Data (SIMD) machines by interpretation. The control unit would continuously issue the signals necessary for interpreting the instruction set. A processing element (PE) would only participate in the part of the loop which necessary for interpreting its instruction, while remaining idle in the parts which are not. In this thesis, a model of the interpretation cycle used in MIMD interpretation on SIMD machines is formulated. This model is then used to study the problem of Variable Instruction Issue (VII), where different subsets of the instruction set being interpreted, rather than the complete instruction set, are issued in order to enhance the performance of the interpretation process. The problem of choosing these subsets has been shown to be NP-Complete. Heuristics that provide near optimal solutions are developed and analyzed. These heuristics have shown considerable speedup over non-variable interpreter loops. Finally, various extensions to the model, and their effects on the analysis are also presented and studied. These include extensions to handle pipelining and functional unit reuse.
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