Author: Tom Likens
Date: 11:26:04 03/24/04
Go up one level in this thread
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. --tom
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