Using Emulations to Enhance the Performance of Parallel Architectures

AbstractÐWe illustrate the potential of techniques and results from the theory of network emulations to enhance the performance of a parallel architecture. The vehicle for this demonstration is a suite of algorithms that endow an N-processor bit-serial processor array A with a ªmeta-instructionº GAUGE k, which (logically) reconfigures A into an N=k-processor virtual machine Bk that has: 1) a datapath and memory bus whose emulated width is k bits, as opposed to A's 1-bit width and 2) an instruction set that operates on k-bit words, in contrast to A's instruction set, which operates on 1-bit words. In order to stress the strength of the approach, we show (via pseudocode) how our emulation techniques can be implemented efficiently even if A operates in strict SIMD mode, with only single-bit masking capabilities and with no indexed memory accesses. We describe at an algorithmic level how to implement our techniqueÐincluding datapath conversion (ªcorner-turningº) and the creation of the word-parallel instruction setsÐon arrays of any regular network topology. We instantiate our technique in detail for arrays based on topologies with quite disparate characteristics: the hypercube, the de Bruijn network, and a genre of mesh with reconfigurable buses. Importantly, the emulations that underlie our technique do not alter the native machine's instruction set, hence allowing an invariant programming model across gauges. Index TermsÐParallel architecture, multiprocessor interconnection, parallel algorithms.