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Bill Carson Permalink
November 23, 2011, 22:30

Wrong! There is no evidence to conclude that the Ackermann function is slower growing than the Busy Beaver Sigma.
The fact that a function is not computable doesn't necessarily mean it needs to be fast growing (e.g. convert the halting problem to a function that returns a boolean: not very fast growing, is it?)

Comment Responses

November 25, 2011, 23:08

Ackermann function is a computable function and for any computable function f(BBSigma(n)) < BBSigma(n+1).

Thomas Permalink
March 07, 2012, 14:20

Bill is right about there being no evidence that the Ackermann function grows slower than a non-computable function in general, but for the busy beaver function there is a proof that it grows faster than any computable function. See the wikipedia article for a proof.

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