Author: Inmann Werner
Date: 11:58:10 10/03/99
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On October 03, 1999 at 09:24:59, Georg v. Zimmermann wrote: >Almost every program uses extension after checks or after capture-moves. Some >programs have other search-extensions as well. >Has anyone tried a "extend if same piece moved twice" ? >That would help a lot in >1.) endgame pawn races >2.) closed positions where you want to manuever one piece to a certain position >3.) Checks by repetition (if not covered by check extension). > >Regards, > >Tec. Be careful with extensions. A chess engine tries all moves, also the stupid ones, and so you also extend all the stupid moves exploding the tree. I tried to extend one full ply, if a passed pawn moves. Thought it as a good idea in endgames and failed. Everything got very, very slow. The program found some positions very quick, but over all, it was really bad, because to specialized. Another attempt was something like singular check answer extension (hope the right word?). I extend, if there is a check and the king only has one move. The extensions really works good. Then I tried to extend also, if the king gets checked and no beating move avoids mate, so the king has to move. There were some thoughs behind it about running mates and horizon effect. I tried it with testpositions and it worked really good. Then I tried it in matches and......, forget it! Also a long time, a had the full Null Move extension in my program. Again, in testsuites it was great, but in matches it slowed and was not so impressive. I tuned it down a little, so now it works pretty good sometimes and not expanding the tree too much. Extensions are tricky and have to be tested in games. Testsuites are the wrong place for them. In most testsuites there is a "solve" move leading to mate. In games, you do not see this so much, but have to find "only" some good move... Thats different IMHO. Werner
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