A heuristic fault-tolerant routing algorithm in mesh using rectilinear-monotone polygonal fault blocks

A new, rectilinear-monotone polygonally shaped fault block model, called Minimal-Connected-Component (MCC), was proposed in [D. Wang, A rectilinear-monotone polygonal fault block model for fault-tolerant minimal routing in mesh, IEEE Trans. Comput. 52 (3) (2003) 310-320] for minimal adaptive routing in mesh-connected multiprocessor systems. This model refines the widely used rectangular model by including fewer non-faulty nodes in fault blocks. The positions of source/destination nodes relative to faulty nodes are taken into consideration when constructing fault blocks. Adaptive routing algorithm was given in Wang (2003), that constructs a minimal "Manhattan" route avoiding all fault blocks, should such routes exist. However, if there are no minimal routes, we still need to find a route, preferably as short as possible. In this paper, we propose a heuristic algorithm that takes a greedy approach, and can compute a nearly shortest route without much overhead. The significance of this algorithm lies in the fact that routing is a frequently performed task, and messages need to get to their destinations as soon as possible. Therefore one would prefer to have a fast answer about which route to take (and then take it), rather than spend too much time working out an absolutely shortest route.