Fully Persistent Arrays for Efficient Incremental Updates and Voluminous Reads

Fully Persistent Arrays for Efficient Incremental Updates and Voluminous Reads (1992)

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by Tyng-Ruey Chuang

Venue:	4th European Symposium on Programming
Citations:	5 - 2 self

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Datum	Value	Source
TITLE	Fully Persistent Arrays for Efficient Incremental Updates and Voluminous Reads	SVM HeaderParse 0.1
AUTHOR NAME	Tyng--ruey Chuang	SVM HeaderParse 0.1
AUTHOR ADDR	; Author's address: 251 Mercer Street, New York, NY 10012, U.S.A. E--mail	SVM HeaderParse 0.1
ABSTRACT	The array update problem in a purely functional language is the following: once an array is updated, both the original array and the newly updated one must be preserved to maintain referential transparency. We devise a very simple, fully persistent data structure to tackle this problem such that ffl each incremental update costs O(1) worst--case time, ffl a voluminous sequence of r reads cost in total O(r) amortized time, and ffl the data structure use O(n + u) space, where n is the size of the array and u is the total number of updates. A sequence of r reads is voluminous if r is \Omega\Gamma n) and the sequence of arrays being read forms a path of length O(r) in the version tree. A voluminous sequence of reads may be mixed with updates without affecting either the performance of reads or updates. An immediate consequence of the above result is that if a functional program is single--threaded, then the data structure provides a simple and efficient implementation of functional arrays. This result is not new. What is new is that many multi--threaded functional array applications also exhibit the incremental updates /voluminous reads execution pattern. Those applications can also be efficiently implemented by the proposed data structure. A comparison of our method to previous approaches to the array update problem is briefly discussed. Empirical results have been collected to measure the effectiveness of the proposed data structure. 1	SVM HeaderParse 0.1
CITATIONS	27 found	ParsCit 1.0