Fault Reconfiguration for the Near Neighbor Task in a Multistage-Network MIMD System

Abstract

Dynamic fault reconfiguration in an MIMD environment with a multistage interconnection network is considered. The near neighbor class of problems, which involve fundamental parallel processing algorithms such as partial differential equations and low level image processing algorithms, are chosen as the target application in such an environment. It is shown that dynamic fault reconfiguration can be achieved efficiently without any additional or modified hardware in case of (permanently) faulty processors. Two types of multistage networks are considered: general multistage networks (such as Benes networks) and the Omega network. The communication time of the system with faulty processors is minimized by rearranging the order in which the fault-free processors communicate with each other. For any number of faults, a reconfigured system with a general multistage network is shown to require an increase from four to five data transfers for each iteration of the near neighbor problem. For the Omega network, many faults can be handled by six data transfers, but in some cases up to 10 data transfers are necessary. In order to minimize the computation time of the system with faults, the data points of faulty processors are distributed equally and in parallel among the remaining processors. The technique used for parallel data distribution is called Uniform Data Distribution.