Task Migration In Hypercube Multiprocessors

Allocation and deallocation of subcubes usually result in a fragmented hypercube where even if a sufficient number of hypercube nodes are available, they do not form a subeube large enough to execute an incoming task. As the fragmentation in conventional memory allocation can be handled by memory compaction, the fragmentation problem in a hypercube can be solved by task migration, i.e., relocating tasks within the hypercubc to remove the fragmentation. The procedure for task migration closely depends on the subcube allocation strategy used, since active tasks must be relocated in such a way that the availability of subcubcs can be detected by that allocation strategy. In this paper, we develop a task migration strategy for the sub cube allocation policy based on the binary reflected Gray code. A goal configuration (of destination subeubes) without fragmentation is determined first. Then, the node-mapping between the source and destination subcubes is derived. Finally, a routing procedure to achieve shortest deadlock-free paths for relocating tasks is developed.