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Subject: Re: Iterative deepening -- Why add exactly one ply?

Author: Tord Romstad

Date: 09:30:33 05/26/04

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On May 26, 2004 at 12:13:03, Robert Hyatt wrote:

>On May 26, 2004 at 10:53:16, Stefano Gemma wrote:
>
>>I've used an recursive-iterative deepening. I try to explain in my poor english.
>>At any N plyes i've applyed iterative deepening as for the root. Suppose to
>>start with 2 plies. The next iterations you should search 4 then 6 then 8 plies
>>etc, form the root. But, when you're searching 8 plies depth, and you are at a
>>position located at ply 2, why don't use iterative deepening starting from ply
>>2, instead to do a full search of the remaining 6 plies? So i've tried to
>>consider positions at ply 2 (and 4 and 6...) as they were at the root, and start
>>a search to ply 4, then 6, then 8. Sometimes works better, sometimes worse...
>>
>>I have tried different schemas, in Raffaela. The best seems the schema 2-4. You
>>increment the iterative deepening by 2 plies (one chess move by colour) and, for
>>any ply, you make an iterative deepening with increment 4. In some position, 2-2
>>was better.
>>
>>I've abandoned this idea, for now, because i'm working on a new engine and i've
>>little time for my hobby, but i think that could be interesting.
>>
>>Ciao!!!
>>
>>Stefano Gemma
>
>
>That sounds like an interesting idea that is worth testing.  IE at _any_ ply
>where you want to do a depth=N search, you iterate and do a depth=1, 2, ..., N
>to work your way up to that point.  With luck the  depth 1 to n-1 searches will
>be cheap with hash information, if there is none, move ordering will probably be
>broken anyway and this might improve things.

This is exactly what I always thought was called "internal iterative
deepening", but I have recently learned that others use this term to refer
to something different.

I use something similar to Stefano's technique (if I understood it correctly)
at all internal nodes where the remaining depth is high (currently 5 plies or
more) and I expect a fail high.

Tord



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