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The Generation of Permutations in Magnetic Bubble Memories

In this paper two recent models of basic operations in magnetic bubble memories are discussed. The accessing of an item and the generation of arbitrary permutations in these models are studied. It is shown that the two methods of accessing an item as described in this paper for the two models are optimal in terms of the number of operations. For each model, lower bounds for the number of operations needed to generate arbitrary permutations are derived for both the worst case and the average case. Consequently, the methods proposed in this paper for both models are shown to be optimal as far as the order of magnitude of the number of operations is concerned. The results obtained in this paper may be helpful for deciding upon the relative merits of these two models.