**From:** Stuart Armstrong (*dragondreaming@googlemail.com*)

**Date:** Wed Sep 17 2008 - 08:30:49 MDT

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*> I think you are right that we can't distinguish between code and data. If we use the definitions in my paper then there is no difference between RSI (the program rewriting itself) and a simple program with a goal (meaning that the utility of the output would increase if its run time limit were relaxed).
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*> So how could RSI be defined in a meaningful way?
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By engineering, not mathematics. A RSI program with a finite set of

data is mathematically equivalent to a universal Turing machine

running a fixed integer. But this equivalence is virtually never used

in practice, because it's nearly impossible to calculate and nearly

meaningless when you do so!

So a RSI has to be a statement about the actual architecture of a

program, not about the equivalent Turing machine. Your model seems

acceptable as a definition, as far as I can tell (there will be

others). A heuristic definition of RSI could be a program in an

architecture that returns, after some time, to state similar to the

one it started with, except with an improvement. The formal definition

would be given by specifying this architechture. For instance, you

could demand that a program has to start in a certain isolated

computer, with a certain amount of free space, always accepting

certain inputs. Subject to these constraints, a RSI makes sense.

As an aside, the restriction from Kolmogorov complexity in your paper

isn't actually very restrictive. Real programs are hopelessly

inefficient for their length, even more so if you break them down into

machine code. There are vast possibilities for improvement; for

instance, P1 could incoporate the instruction "first, wait ten million

years, then start doing stuff", and each subsequent P knocks one year

off this total. The Kolmogorov complexity of P10 000 000 is slightly

lower than P1, but I know which program I'd want to use...

Stuart

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