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Richard E. Ladner

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16 papers
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16

FOCS Conference 1994 Conference Paper

Optimizing Static Calendar Queues

  • K. Bruce Erickson
  • Richard E. Ladner
  • Anthony LaMarca

The calendar queue is an important implementation of a priority queue which is particularly useful in discrete event simulators. In this paper we present an analysis of the static calendar queue which maintains N active events. A step of the discrete event simulator removes and processes the event with the smallest associated time and inserts a new event whose associated time is the time of the removed event plus a random increment with mean /spl mu/. We demonstrate that for the infinite bucket calendar queue the optimal bucket width is approximately /spl delta//sub opt/=/spl radic/(2b/c)/spl mu//N where b is the time to process an empty bucket and c the incremental time to process a list element. With bucket width chosen to be /spl delta//sub opt/, the expected time to process an event is approximately minimized at the constant c+/spl radic/(2bc)+d, where d is the fixed time to process an event. We show that choosing the number of buckets to be O(N) yields a calendar queue with performance equal to or almost equal to the performance of the infinite bucket calendar queue. >

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TARK Conference 1986 Conference Paper

The Logic of Distributed Protocols

  • Richard E. Ladner
  • John H. Reif

A propositional logic of distributed protocols is introduced which includes both the logicof knowledge and temporal logic. Phenomena in distributed computing systems such as asynchronous time, incomplete knowledge by the computing agents in the system, and game-like behavior among the computing agents are all modeled in the logic. Two versions of the logic, the linear logic of protocols (LLP) and the tree logic of protocols (TLP) are investigated. The main result is that the set of valid formulas in LLP is undecidable. iResearchsupportedby the NationalScienceFoundationGrant No. DCR-8402566. ~Researchsupportedby the Officeof NavalResearchContractNo. N00014-80~C-0647.

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FOCS Conference 1983 Conference Paper

Estimating the Multiplicities of Conflicts in Multiple Access Channels (Preliminary Report)

  • Albert G. Greenberg
  • Richard E. Ladner

A conflict of multiplicity k occurs when k stations transmit simultaneously to a multiple access channel. As a result, all stations receive feedback indicating whether k is 0, 1, or is ≥ 2. If k = 1 the transmission succeeds, whereas if k ≥ 2 all the transmissions fail. In general, no a priori information about k is available. We present and analyze an algorithm that enables the conflicting stations to cooperatively compute a statistical estimate of k, at small cost, as a function of the feedback elicited during its execution. An algorithm to resolve a conflict among two or more stations controls the retransmissions of the conflicting stations so that each eventually transmits singly to the channel. Combining our estimation algorithm with a binary tree algorithm leads to a hybrid algorithm that resolves conflicts faster on average than any other reported to date.

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