Author: Uri Blass
Date: 09:53:33 01/03/06
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On January 03, 2006 at 12:18:58, Tord Romstad wrote: >On January 03, 2006 at 11:49:05, Robert Allgeuer wrote: > >>On January 03, 2006 at 10:49:54, Maurizio Monge wrote: >> >>>What you said is surely true. >>>But what i find strange is that, IIRC, the only quite new technic in computer >>>chess that can be found in fruit is history pruning, everything else is just a >> >>History pruning was already in use in SmarThink and other engines before as >>well. If I am not completely mistaken history pruning was invented by Sergej for >>SmarThink. > >It is possible that Sergei introduced the name "history pruning", but the >technique itself is very old; certainly much older than SmarThink. You are right and Movei use it for some years. First public version of movei to use history based reduction was 07_99 I did not talk about it at that time but I used it and I am not going to be surprised if other also used it earlier. I no >longer remember where or when I heard about it for the first time, but it was >definitely not in this millennium. > >"History pruning" is a really bad name for the technique, by the way. Since >a long time, I have been advocating to rename it to "late move reductions". > >The word "history" is misleading because the technique can be implemented >without using history counters. In this case it is not history based pruning. I certainly use history counters but it is possible that I can improve it by not using history counters and using different conditions instead of them. Today I use combination of evaluation and history information to decide about reduction. I currently use a combination of null move >threat detection and evaluation data to make my late move reduction decisions, >and don't use history counters at all. This seems to work clearly better, >at least in my program. originally when I implemented it I had no condition about late move reduction but later I changed it and at least today I never reduce the first move. > >The word "pruning" is misleading because most people don't use the idea >to prune moves, but only to reduce the search depth. I agree that the word reduction is better. > >"Late move reductions" is a much more appropriate name, and does a better >job of explaining what the idea is about: Reducing the depth for the less >interesting moves late in the move list. > >Tord The idea is to reduce the depth of moves that you are almost sure that they are going to fail low. Uri
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