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

Author: Robert Hyatt

Date: 10:34:23 05/26/04

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On May 26, 2004 at 12:30:33, Tord Romstad wrote:

>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

I have used "IID" for years, but in a very restricted way, namely to handle the
case along the PV where I have no hash move.  I've never tried it _everywhere_
before, so have no data.  But I intend to try to see if it is something that
could work, or if it is a waste...





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