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AI Challenge Forums • View topic - Congratulations a1k0n!

It is currently Sun Dec 17, 2017 5:44 pm Advanced search

Congratulations a1k0n!

Random stuff about the contest, posts that don't fit in the other forums.

Re: Congratulations a1k0n!

Postby ebrahim » Mon Mar 01, 2010 10:39 pm

Congratulations to you, and to your son whose father is a hero ;-)
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Re: Congratulations a1k0n!

Postby DjinnKahn » Mon Mar 01, 2010 10:49 pm

DjinnKahn
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Re: Congratulations a1k0n!

Postby grogers » Tue Mar 02, 2010 12:31 am

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Re: Congratulations a1k0n!

Postby aramadia » Tue Mar 02, 2010 1:10 am

The transposition part of the lookup table is only useful for deep searches. The true power is storing the best move computed from a lower ply and using it again in a higher ply search to trigger an early alpha beta cutoff (see move ordering). This can nearly double your search depth.
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Re: Congratulations a1k0n!

Postby aramadia » Tue Mar 02, 2010 1:21 am

Another amazing benefit (when used in combination with iterative deepening), you can get another huge boost by saving the table between moves. If you searched 20 ply in one move, its possible that half of the data is still useful for the next move. You only need to search 2 more plies as opposed to doing the first 18. Yes, the tree is exponential but with good pruning the branch factor is less than 1.5, so your hashtable becomes a sort of cache. This technique adds 4-6 plies but I had a bug in my code so I had to remove this feature at the last second.

I'm sure if a1k0n implements this, his bot will become quite formidable.

Implementation Details:
Must use some kind of fast hashing scheme (see Zorbist) that allows you to "undo" your moves. Before this I realized I spent 50% of my cpu time hashing.

It isn't necessary to store the entire board in the hashtable, just use a 64 bit key and accept the possibility of hash collisions. The probability of collision with a perfect hash (which Zorbist nearly is) is 50% after 5.1 Billion hashes. (see http://en.wikipedia.org/wiki/Birthday_attack). This allows you to store each entry in about 20 bytes, give it great cache locality. (as opposed to 100MB+ tables)
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Re: Congratulations a1k0n!

Postby dmj » Tue Mar 02, 2010 1:55 am

a1k0n, great job!

Everyone else, not too shabby either :) Without a1k0n, there would have been a rumble at the top.

Its been fun, everyone. I look forward to learning more on the forums!
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Re: Congratulations a1k0n!

Postby analyst74 » Tue Mar 02, 2010 4:17 am

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Re: Congratulations a1k0n!

Postby DjinnKahn » Tue Mar 02, 2010 5:05 am

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Re: Congratulations a1k0n!

Postby barank » Tue Mar 02, 2010 5:57 am

Congratz a1k0n , really good job !
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Re: Congratulations a1k0n!

Postby Accoun » Tue Mar 02, 2010 10:14 am

a1k0n, u lucky because that organizers hate me
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