Pebbling with an Auxiliary Pushdown

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Mathematics (HMC)

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A pebble game on graphs is introduced which bears the same relationship to the ordinary pebble game as auxiliary pushdown machines bear to ordinary machines. The worst-case time-space trade-off for pebbling with an auxiliary pushdown is shown to be [image] (where T denotes time, S denotes space and N denotes the size of the graph), which contrasts with [image] for ordinary pebbling. The significance of this result to various questions concerning relations among complexity classes is discussed.

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© 1981 Elsevier Ltd.

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