Author: Uri Blass
Date: 11:11:44 08/17/03
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On August 17, 2003 at 13:58:52, Tord Romstad wrote: >On August 16, 2003 at 17:43:09, Uri Blass wrote: > >>On August 16, 2003 at 17:17:26, Tord Romstad wrote: >> >>>The last few weeks I have been experimenting with MTD(f). It still does not >>>work quite as well >>>as my old aspiration alpha beta search, but I intend to keep working on it for >>>some more time. >>> >>>One of my biggest worries right now is that the search slows down almost to a >>>full stop when >>>the hash table starts getting full. For instance, here are the time (in >>>seconds) needed to >>>finish a 11-ply search from the starting position for different hash table sizes >>>from 5 to 320 MB: >>> >>>5MB: 102 seconds >>>10MB: 88 seconds >>>20MB: 78 seconds >>>40MB: 55 seconds >>>80MB: 47 seconds >>>160MB: 34 seconds >>>320MB: 27 seconds >>> >>>Is this normal, or do I have some kind of bug? I really hope I don't need a >>>320MB hash table >>>to play decently at slow time controls. Should I take a look at my hash table >>>replacement >>>scheme? Currently I always replace if the depth of the new position is >= dept >>>of old >>>position. >>> >>>Another problem is that MTD(f) has very weird effects when combined with the >>>various forward >>>pruning techniques I use. This is not entirely unexpected, because I use the >>>values of alpha >>>and beta for pruning decisions. When I replace plain MTD(f) (which I haven't >>>been able to >>>make work very well; too many researches) with MTD(f) with a convergence >>>accelerator, I >>>often get entirely different search results for the same position. If I remove >>>all selectivity >>>(except null move pruning) from my search, changing the test driver does not >>>have any >>>effect on the search results, but then my program becomes much too slow. I >>>suppose I >>>will have to work out new forward pruning techniques. >>> >>>Tord >> >>Why? >>Maybe your forward pruning is superior to MTD. >> >>The fact that MTD is not good for you because of your forward pruning does not >>mean that your forward pruning is bad. > >I don't really like my forward pruning. I am beginning to become sceptical to >all >pruning schemes which involve the values of alpha or beta. Even in plain >aspiration >search there are problems when such pruning is combined with hash tables. I guess that not for me because I do not use the hash tables for pruning. I also use alpha or beta for my pruning decisions and I plan to add in the future more rules that are going to use alpha and beta. Uri
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