Norman Samish writes:
>http://arxiv.org/abs/nlin.AO/0506030 shows the following abstract,
>suggesting that complex computations are not precisely repeatable. Doesn't
>Bruno's Computation Hypothesis imply that computations ARE precisely
>repeatable?
>
>"Modern computer microprocessors are composed of hundreds of millions of
>transistors that interact through intricate protocols. Their performance
>during program execution may be highly variable and present aperiodic
>oscillations. In this paper, we apply current nonlinear time series
>analysis
>techniques to the performances of modern microprocessors during the
>execution of prototypical programs. While variability clearly stems from
>stochastic variations for several of them, we present pieces of evidence
>strongly supporting that performance dynamics during the execution of
>several other programs display low-dimensional deterministic chaos, with
>sensibility to initial conditions comparable to textbook models. Taken
>together, these results confirm that program executions on modern
>microprocessor architectures can be considered as complex systems and would
>benefit from analysis with modern tools of nonlinear and complexity
>science."
Isn't the noise in the system (with ensuing unpredictable behaviour) one of
the main limits to how densely packed circuits on a chip can be? If
computations are not precisely repeatable, then what is to stop my computer
from garbling this email and sending it to some random destination? Now, in
the case of complex analogue systems like human brains, it would be a
different matter: you would expect classical chaos to have an effect, and
different brain states might result even given the same inputs (or no
inputs). We expect this unpredictability from people, but if our machines
start behaving in a similar fashion, we assume that they're broken or
incompetently designed. Is this an unfair double standard?
--Stathis Papaioannou
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Received on Mon Jul 11 2005 - 21:28:50 PDT