Author: José Carlos
Date: 16:36:50 01/05/04
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On January 05, 2004 at 19:24:31, Bas Hamstra wrote: >On January 05, 2004 at 08:48:23, José Carlos wrote: > >> Hi, I'd like to try singular extensions in my program. I've been trying to >>think about it and all my tries so far result in worse performance. After some >>web search I haven't been able to find anything but the general idea described. >> Is there any good description somewhere? Some pseudo-code? I guess there must >>be something interesting in the archives but I can't download all of them. >> Thanks in advance, >> >> José C. > >Here is what I tried (idea from Bruce I believe): > >Before you search all moves (after nullmove) you search all moves (unsorted) >with D-R Good point I had missed :) I was doing an expensive D search with (Alpha-Margin,Alpha-Margin+1) and if only one move failed high, search it again with (Alpha,Beta) extended 1 ply. >and check if there is one and only one move with a score above alpha >*and* above Alpha-Margin. So if I get it right, you search all moves with D-R and a null window around Alpha-Margin. If only one move fails high, then search it again with D-R and a null window around Alpha. If it fails high again, then that move is extended. >If so, in the normal search to depth D extend that >move. I did not do this in nullwindow searches, or else performance crashed. I've had problems when making this difference. For example, I used to not try null move in PV nodes. At some point, I realized that a non PV move failed high, then was researched with an open window and failed low due to not applying a null move threat extension! >No great results. In particular I didn't see much spectacular long pv's show up. > >I am interested in refinements or other approaches. And are there good >testpositions to check the effect of SE? Thanks for the tips. I'll report my results if I manage to make it work. José C. >Best regards, >Bas.
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