Author: Richard Pijl
Date: 14:29:19 03/24/04
Go up one level in this thread
On March 24, 2004 at 16:44:12, Tord Romstad wrote: >On March 24, 2004 at 14:26:04, Tom Likens wrote: > >>On March 24, 2004 at 05:39:20, Tord Romstad wrote: >> >>>On March 24, 2004 at 05:17:56, Peter Fendrich wrote: >>> >>>>Uri didn't invent ETC if that's what you imply! >>>> >>>>Given your story about costly move/unmove functions it's possible that ETC gives >>>>you some savings. Without ETC you will hit the cutoff anyway in the child node >>>>and with smaller unmove costs ETC is not that effective IMHO. >>> >>>It seems to me that you miss part of the idea of ETC. You are right that >>>you will get the cutoff in the child node even without ETC, but in which >>>child node? If your move ordering is not perfect, there is a risk that >>>you will have to search many moves before you get the cutoff. When you >>>use ETC, you check the hash values for *all* child nodes before you >>>start searching, which can sometimes save a lot of nodes. >>> >>>To me, ETC has always been a clear win. The last time I made any >>>experiments, it reduced my tree size by about 10% at high search depths. >>>I am fairly sure it is a technique which works better with MTD(f) than >>>with more conventional search algorithms, though. >>> >>>Tord >> >>How do you handle extensions? Currently, most of my extensions are >>set after the engine moves and since the extensions affect the draft >>(which in turn affects the validity of the hash match) it seems like this is >>a problem. This might be workable (in my current scheme) if I started >>tracking the extensions that were triggered by a move in the hash >>table. > >You are right, this is a problem. My "solution" is to ignore the problem >and hope it isn't too important in practice. > My solution to that problem is not to do a cutoff, but order the cutoff move first in the movelist. That way the regular search will find the cutoff move as the first move. Richard.
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