Author: Tord Romstad
Date: 14:34:20 03/24/04
Go up one level in this thread
On March 24, 2004 at 17:29:19, Richard Pijl wrote: >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. That's not a bad idea -- Thanks for the suggestion! :-) Tord
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