Author: rasjid chan
Date: 03:59:58 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 Thanks. I think there is much more to ETC. I'll see what can be done like checking only good moves, etc.. . nothing is simple otherwise all programs == Gothmog. An aside - immediately after I implemented my pseudo ETC, after hash_cutoff_before_makemove()... I tested it against Gothmog at 60 moves / 40 secs. No need tournament time as Gothmog, Ktulu, Ruffian almost never fail whatever time control. Pseudo or otherwise, it plays very differently and I don't yet know why, sometimes making moves almost instantly which was not noticeable in the past. Gothmog was nearly caught but my program finally conceded a draw from a clearly winning positions. Very rare but can happen,mainly because my program has yet to reach anything call strong.I mention this because I have some impressions about the 3 programs;seemingly Ruffian is the strongest, Ktulu and Gothmog don't yet seem miles apart. I think Gothmog has some lopeholes somewhere that allow clearly weaker programs to occasionaly sneek pass. My guess is Gothmog seem to have very aggressive kingsafety that sometimes backfire, or maybe the assymetry you metioned before. Rasjid
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