A Note on Implementing Combining Networks

In shared memory multiprocessors combining networks serve to eliminate hot spots due to concurrent access to the same memory location Examples are the NYU Ultracomputer the IBM RP and the Fluent Machine We present a problem that occurs when one tries to implement the Fluent Machine s network nodes with network chips that do not know their position within the network We formulate the problem mathematically and present two solutions The rst solution requires some additional hardware around nodes that can be put outside network chips The second solution requires a minor modi cation of the routing algorithm but one can prove that there is no performance loss