The routing problem in transputer-based parallel systems

The availability of a robust and reliable routing support is of primary importance in transputer-based parallel systems. The difficulties in the design of such a software system lie mainly in the necessity of guaranteeing the absence of communication deadlocks between its component processes. Many techniques have recently been proposed in the literature for solving this problem, but until now they seem to have been rarely used in practical applications. The paper expounds the theory needed for setting up a general-purpose routing support. First, the essential features of a routing system are sketched and the main techniques and solutions available are briefly surveyed, highlighting their advantages and limits of applicability. Then a graphical representation of the program data exchanges, the I/O graph, which makes it possible to detect potential deadlock conditions, is introduced. Its application in the design of a deadlock-free routing system for squared mesh networks is given by way of an example. Finally, some transputer-dependent implementative issues are discussed, showing how to improve the routing support performance.