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Subject: Re: O(1) garbage

Author: Dann Corbit

Date: 10:11:35 05/17/01

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On May 17, 2001 at 08:39:35, Alberto Rezza wrote:

>On May 16, 2001 at 19:12:23, Dann Corbit wrote:
>
>>Chess is finite.  TSP is finite.  Matrix multiplication is finite.  All
>>algorithms are finite.  Otherwise, they AREN'T algorithms.
>
>Come on, Dann. Termination of algorithms and finiteness of a game are
>two totally unrelated matters. Is that so difficult to understand?

I think I understand it perfectly.  You have algorithms, and you can give them
an instance of data.

>If chess is too much, try with tic-tac-toe. A few hundred nodes, and
>you cannot increase the depth anymore: all leaves are won, lost or
>drawn, there is nothing left to expand. It is finite, so it is O(1)
>time. And chess is the same, for the same reason.

The algorithm for tic-tac-toe can be a table lookup, a brute force search,
alpha-beta, etc.  Since the problem is so small (there are only 9^3 states, and
many of them are thrown out as illegal) the exponential nature of even brute
force search is unimportant.  That's because n=9, and it is not insufferable.
You could easily create a table of all possible correct moves.  Then tic-tac-toe
game is O(1).

Once again, this is an example of how to decide what is computable.  Since
'noughts and crosses' has a tiny n for input, it *is* computable no matter how
you do it.

The ALGORITHM of how you solve tic-tac-toe can have many different kinds of
behavior, depending on what algorithm you choose.

I truly fear for the future of corporate computation, because nobody understands
the practical importance of complexity.

>With matrix multiplication, after multiplying two nxn matrixes, you
>can always find two (n+1)x(n+1) matrixes to try. The algorithm WILL
>terminate, but it will take longer: for any time duration T, you can
>find an input large enough that it takes more than T to compute, so it
>is not O(1).

I have said all that I will say to you on this matter.  If you wish to discuss
it further, you will have to send me an email.



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