Performance of 4-dimensional PANDORA networks

The Melbourne University Optoelectronic Multicomputer Project is investigating dense optical interconnection networks capable of providing low latency data transfers of small data items. Such capabilities are useful in the exploitation of small grain parallelism. In many cases, reducing the grain size of tasks increases the amount of parallelism which can be found in the program. Our networks use an organization of data transfers called PANDORA (PArallel Newscasts on a Dense Optical Reconfigurable Array). The communication patterns on a PANDORA network are pre-determined, removing the overhead of sending and decoding addressing information. Instead the data is recognized by the time of arrival and the channel on which it arrives. Previous efforts have focused on 2-dimensional multiple broadcasting networks where each node may broadcast a different data item on the row and columns of the network. For large processor arrays, we have to reduce the density of the interconnection network as full interconnection on each row becomes too expensive. This paper discusses a 4-dimensional network which achieves a significant reduction in density with only a small increase in data transfer delays