Parallel Algorithms and Architectures pp 155-162 | Cite as

# On reliable networks from unreliable gates

## Abstract

The study of networks with small error probability was inaugurated by J.v. Neumann in [1] in 1952. Assume there is a complete set of (unreliable) gates with error probability ɛ smaller than 1/2. One of the central results in this field (argued heuristically by von Neumann and proved rigorously by R.L. Dobrushin and S.I. Ortyukov [5] in 1977) is the following: Let γ be any (extremely small) positive constant. Further let A be a network realizing Boolean function f provided no gate has failed. (The error probability of A may be very great.) Let C(A) be the complexity of A (i.e. the sum of "costs" of its elements). Then the function f can be realized by a (reliable) network Ã with error probability not greater than ɛ+γ and complexity O(C(A)logC(A)). N. Pippanger [2] showed in 1985 that for almost all Boolean functions f there are networks Ã with complexity O(C(A)) instead of O(C(A)logC(A)). The proof is very easy and ingenious. Note that O(C(A)) means the following: There is a constant c_{1} such that C(Ã)≤c_{1}C(A). Constant c_{1} was not determined by Pippenger, but it seems to be very great. We show that there is a constant c_{2}=c_{2}(ɛ) such that C(Ã)≤c_{2}C(A), where c_{2}(ɛ) → 1 if ɛ → 0. Thus, for almost all Boolean functions networks constructed by our method have very small error probabilities (near that of the elements) and almost minimal complexity.

## Keywords

Input Vector Boolean Function Error Probability Small Positive Number Reliable Network## Preview

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## References

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