USE OF MEAN DISTANCE BETWEEN OVERFLOW RECORDS TO COMPUTE AVERAGE SEARCH LENGTHS IN HAS FILES WITH OPEN ADDRESSING
Abstract
Average search lengths are calculated using both the well known Poisson
distribution for the number of addresses assigned a number of records, and
an empirical expression for the mean distance between overflow records
with the same home address. The method involves computing the number of
disk accesses required to randomly retrieve y records overflowing from
a given home address, using a knowledge of the mean distance between
overflow records. The Poisson distribution is then used to obtain the
total accesses required to retrieve all records in the file, from which
the average search length may be deduced. The average search length
values obtained agree well with the experimental results of Peterson, and
the method can be recommended for use in practical design situations.
Values of mean distance between overflow records for different loading
factors and address capacities are also predicted.
Description
Keywords
Computer Science