Author: Robert Hyatt
Date: 09:13:03 05/26/04
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On May 26, 2004 at 10:53:16, Stefano Gemma wrote: >On May 25, 2004 at 07:59:33, Tord Romstad wrote: > >>In all implementations of iterative deepening I have seen, the search depth >>is always incremented by exactly one ply between each iteration. Is there any >>reason to believe that this is optimal? Has anybody tried other increments? >> >>I am now running some tests with an increment of 3/4 of a ply. So far, the >>results don't seem very different from the usual 1 ply increment. If it turns >>out that increments different from 1 ply are no worse, this could perhaps be >>useful in time management. The engine could use 1 ply increments most of the >>time, but occasionally add only half a ply if just a small amount of the >>allocated thinking time is left. >>Any thoughts about this? > >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.
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