NDLI: Space/time trade-offs in hash coding with allowable errors

Content Provider	ACM Digital Library
Author	Bloom, Burton H.
Abstract	In this paper trade-offs among certain computational factors in hash coding are analyzed. The paradigm problem considered is that of testing a series of messages one-by-one for membership in a given set of messages. Two new hash-coding methods are examined and compared with a particular conventional hash-coding method. The computational factors considered are the size of the hash area (space), the time required to identify a message as a nonmember of the given set (reject time), and an allowable error frequency.The new methods are intended to reduce the amount of space required to contain the hash-coded information from that associated with conventional methods. The reduction in space is accomplished by exploiting the possibility that a small fraction of errors of commission may be tolerable in some applications, in particular, applications in which a large amount of data is involved and a core resident hash area is consequently not feasible using conventional methods.In such applications, it is envisaged that overall performance could be improved by using a smaller core resident hash area in conjunction with the new methods and, when necessary, by using some secondary and perhaps time-consuming test to “catch” the small fraction of errors associated with the new methods. An example is discussed which illustrates possible areas of application for the new methods.Analysis of the paradigm problem demonstrates that allowing a small number of test messages to be falsely identified as members of the given set will permit a much smaller hash area to be used without increasing reject time.
Starting Page	422
Ending Page	426
Page Count	5
File Format	PDF
ISSN	00010782 15577317
DOI	10.1145/362686.362692
Journal	Communications of the ACM (CACM)
Volume Number	13
Issue Number	7
Language	English
Publisher	Association for Computing Machinery (ACM)
Publisher Date	2005-08-01
Publisher Place	New York
Access Restriction	One Nation One Subscription (ONOS)
Subject Keyword	Retrieval efficiency Storage layout Searching Hash addressing Hash coding Retrieval trade-offs Storage efficiency Scatter storage
Content Type	Text
Resource Type	Article
Subject	Computer Science Computer Science

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