Showing papers in "CWI quarterly in 1989"

An introduction to input/output automata

Abstract: The input output automaton model has recently been de ned in LT LT as a tool for modeling concurrent and distributed discrete event systems of the sorts arising in computer science Since its introduction the model has been used for describing and reasoning about several di erent types of systems including network resource allocation algorithms communication algorithms concurrent database systems shared atomic objects and data ow architectures This paper is intended to introduce researchers to the model It is orga nized as follows Section contains an overview of the model Section de nes the model formally and examines several illustrative examples concerning candy vending machines Section contains a second example a leader election algo rithm Finally Section contains a survey of some of the uses that have so far been made of the model

Compact distributed data structures for adaptive routing

Abstract: In designing a routing scheme for a communication network it is desirable to use as short as possible paths for routing messages, while keeping the routing information stored in the processors' local memory as succinct as possible. The efficiency of a routing scheme is measured in terms of its stretch factor - the maximum ratio between the cost of a route computed by the scheme and that of a cheapest path connecting the same pair of vertices.This paper presents a family of adaptive routing schemes for general networks. The hierarchical schemes H Sk (for every fixed k ≥ 1) guarantee a stretch factor of O (k2 · 3k) and require storing at most O (knk log n) bits of routing information per vertex. The new important features, that make the schemes appropriate for adaptive use, are applicability to networks with arbitrary edge costs;name-independence, i.e., usage of original names;a balanced distribution of the memory;an efficient on-line distributed preprocessing.