Author: Will Singleton
Date: 10:49:49 02/24/99
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On February 24, 1999 at 07:44:06, Vincent Diepeveen wrote: >On February 24, 1999 at 02:30:21, Will Singleton wrote: > >>On February 24, 1999 at 01:16:56, Sylvain Lacombe wrote: >> >>> >>>I just finished implementing the null move. At first, i thought it wasn't saving >>>much time. Then, i reallize that it does save alot, but only at deeper plys. On >>>the first few plys, i think, it evens slow me down. Is that normal? Am i doing >>>something wrong? >>> >>>I don't use the null move at the first ply, only at the second. It save about >>>40% reaching deep 6. But it takes about 10% more for reaching deep 3 and 4. >>> >>>Hope, you can help. >>> >>>Thanks. >>> >>>Sylvain. >> >>You're probably doing something wrong. But get a second opinion. :) >> >>My prog will use about half as many nodes early on, like up to ply 5, then the >>effect becomes more pronounced, and in plys above 7 or 8 can show 2-3x >>reductions. But it depends on the position. If there's a single best move, >>there's more reduction than if the position is pretty quiet. So try it on a >>couple of different test suites, like wac vs Bratko-Kopec. Or, use the >>positional BK positions measured against the tactical ones (12 each). >> >>Of course you wouldn't use null on the first ply, that would make it kind of >>hard. Are you using a reduction factor of 2? That's the most popular, it >>seems. I'm testing R=3 now, seems to work OK. But stick with 2 to start. >> >>Also, make sure you don't do 2 nulls in a row. And, for testing purposes, you >>should probably limit a null move to one per search (I mean, once the null has >>been done, don't do it again below that node). Then when it's working better, >>test out multiple nulls. >> >>Null moves are susceptible to zug positions, so just disable them in the >>endgame. You can try out better things later. >> >>Don't do null when in check! >> >>There's an open question about allowing nulls in the pv, so look at that. And >>make sure to clear the ep flag after a null. > >This is no open question. Of course always do nullmove. >If it doesn't give cutoff then you still can see whether you need a >mating extension. > >It saves for me a lot anyway. ALWAYS do nullmove, just take care you >don't improve your alfa with it if it fails. Some do that, but i'm >not a big fan of that. Yes, just recently I took the alpha update out, since it seemed to be causing problems on occasion. I don't know that for certain, but in my case, it's working better. Will
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