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Author Reischuk, Rdiger
Source ACM Digital Library
Content type Text
Publisher Association for Computing Machinery (ACM)
File Format PDF
Copyright Year ©1987
Language English
Subject Domain (in DDC) Computer science, information & general works ♦ Data processing & computer science
Abstract The ability of the strongest parallel random access machine model WRAM is investigated. In this model different processors may simultaneously try to write into the same cell of the common memory. It has been shown that a parallel RAM without this option (PRAM), even with arbitrarily many processors, can almost never achieve sublogarithmic time. On the contrary, every function with a small domain like binary values in case of Boolean functions can be computed by a WRAM in constant time. The machine makes fast table look-ups using its simultaneous write ability. The main result of this paper implies that in general this is the “only way” to perform such fast computations and that a domain of small size is necessary. Otherwise simultaneous writes do not give an advantage. Functions with large domains for which any change of one of the $\textit{n}$ arguments also changes the result are considered, and a logarithmic lower time bound for WRAMs is proved. This bound can be achieved by machines that do not perform simultaneous writes. A simple example of such a function is the sum of $\textit{n}$ natural numbers.
ISSN 00045411
Age Range 18 to 22 years ♦ above 22 year
Educational Use Research
Education Level UG and PG
Learning Resource Type Article
Publisher Date 1987-01-01
Publisher Place New York
e-ISSN 1557735X
Journal Journal of the ACM (JACM)
Volume Number 34
Issue Number 1
Page Count 16
Starting Page 163
Ending Page 178


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Source: ACM Digital Library