Get 20M+ Full-Text Papers For Less Than $1.50/day. Start a 7-Day Trial for You or Your Team.

Learn More →

Use of Mean Distance Between Overflow Records to Compute Average Search Lengths in Hash Files with Open Addressing

Use of Mean Distance Between Overflow Records to Compute Average Search Lengths in Hash Files... Abstract Average search lengths for hash files with open addressing have been computed using the well-known Poisson distribution for the number of addresses assigned x records, and a new expression for the mean distance between overflow records overflowing from a common home address. The method involves computing first the number of disk accesses required to randomly retrieve the y records overflowing from any home address, using a knowledge of the mean distance between overflow records on the disk. The Poisson distribution is then used to obtain the total disk accesses required to retrieve all records in the file, from which the average search length, as total accesses divided by total records, may be deduced. The average search length values obtained agree closely with experimental results. Because it also dispenses with the complex mathematics of existing methods, this new method can be recommended for use in practical design situations. A by-product is that values for the mean distances between overflow records for different loading factors and addresses capacities are also predicted. Received February 1985. 
 
 * Computer Science Department, University of Calgary, 250 University Drive, N.W. Calgary, Alberta, Canada, T2N 1N4 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Computer Journal Oxford University Press

Use of Mean Distance Between Overflow Records to Compute Average Search Lengths in Hash Files with Open Addressing

Bradley,, J.
The Computer Journal , Volume 29 (2) – Jan 1, 1986
Download PDF
4 pages

Loading next page...
 
/lp/oxford-university-press/use-of-mean-distance-between-overflow-records-to-compute-average-rO1mvu1ReC

References (0)

References for this paper are not available at this time. We will be adding them shortly, thank you for your patience.

Publisher
Oxford University Press
ISSN
0010-4620
eISSN
1460-2067
DOI
10.1093/comjnl/29.2.167
Publisher site
See Article on Publisher Site

Abstract

Abstract Average search lengths for hash files with open addressing have been computed using the well-known Poisson distribution for the number of addresses assigned x records, and a new expression for the mean distance between overflow records overflowing from a common home address. The method involves computing first the number of disk accesses required to randomly retrieve the y records overflowing from any home address, using a knowledge of the mean distance between overflow records on the disk. The Poisson distribution is then used to obtain the total disk accesses required to retrieve all records in the file, from which the average search length, as total accesses divided by total records, may be deduced. The average search length values obtained agree closely with experimental results. Because it also dispenses with the complex mathematics of existing methods, this new method can be recommended for use in practical design situations. A by-product is that values for the mean distances between overflow records for different loading factors and addresses capacities are also predicted. Received February 1985. 
 
 * Computer Science Department, University of Calgary, 250 University Drive, N.W. Calgary, Alberta, Canada, T2N 1N4

Journal

The Computer Journal – Oxford University Press

Published: Jan 1, 1986

There are no references for this article.