Author: Ed Schröder
Date: 08:59:43 05/27/04
Go up one level in this thread
On May 26, 2004 at 13:34:23, Robert Hyatt wrote:
>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...
Try to use IID in another way. Actually I found 2 ways that perform better than
the original IID idea.
Preamble: RD = remaining depth
R = reduction depth
1) if (RD >= 3) search all moves with R=(RD-2)+(RD/2) then search all moves
again with the full depth. The principle applies only once in an unsorted tree,
thus is not recursive.
2) if (RD >= 3) search a move with R=(RD-2)+(RD/2) and when finished research
that move again with the full depth. The principle applies only once in an
unsorted tree, thus is not recursive.
I have tried RD>=2 too but found that normal move ordering is superior.
Ed
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