An analysis of the hot spot contention and message combining on the simple serial synchronized‐multistage interconnection network

Simple serial synchronized (SSS) multistage interconnection network (MIN) is a processor‐memory connection network that has a high performance/cost ratio, where the packet is inputted and switch synchronously in the MIN, which has a high pass‐through ratio and is composed of simple elements. This paper evaluates the effect of the hot spot contention and the effect of the synchronous bit‐serial (SBS) message combining in SSS‐MIN, by the theoretical analysis based on probability and simulation. In contrast to conventional MIN, there does not arise a complete tree saturation in SSS‐MIN, but an area, to which the access is difficult, is produced according to the relative position to the hot spot contention. From such a viewpoint, an analysis method for the pass‐through ratio is presented, which considers the position of the switching element to the hot spot. It is verified as a result of evaluation that the proposed method of analysis gives a result close to that of simulation, so long as the access to the hot spot and the connection network architecture stay within a practical range. It is also seen that the pass‐through ratio is deteriorated less in SSS‐MIN by the hot spot contention than in the conventional MIN, and the effect can be almost completely eliminated by the SBS message combining. When a multiprocessor system is actually constructed, performance deterioration due to hot spot contention is greater than in the case where only the pass‐through ratio is considered. This can also be eliminated almost completely by the SBS message combining.