Author: Robert Hyatt
Date: 20:29:46 10/04/98
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On October 04, 1998 at 21:21:09, Roberto Waldteufel wrote: > >On October 04, 1998 at 20:24:08, Will Singleton wrote: > >>On October 04, 1998 at 19:06:15, Roberto Waldteufel wrote: >> >>> >>>Hi all, >>> >>>I wonder what reductions various programs use for the null move. I reduce by two >>>plies, but I believe a one-ply reduction may be more usual. However, I have >>>found R=2 produces quite good results in my program. I would like to hear of >>>others' experiences. >>> >>>Best wishes, >>>Roberto >> >> >>Amateur uses r=2, and gets about a ply deeper on average. But I've noticed that >>in positions where there is a clear better move, the node reduction is great, >>and in positions where there is no clear cut better move, the reduction is not >>that great. Of course, you need it most in the latter situation. I'm probably >>doing something wrong. Do you notice anything similar? >> >>Will > >Yes, I have noticed more improvement when one move is clearly best than when >there are many plausible candidates, but I had put that down to the nature of >the null move! If there are many plausible moves, then that leaves fewer >terrible moves to cause null-move cutoffs on the next ply. Do you find the same >effect with R=1 as with R=2? I suspect that nodes with a clearly best move are >just plain easier to handle than the rest. > >Best wishes, >Roberto null move, R=2, works well and has been used in crafty for several years now. But it does cause problems, and definitely won't work if your machine is slow, because depths of 5-6 will crash and burn when you use null-move. The deeper the search, the safer this becomes, and I haven't seen null-move related losses in a couple of years now. But early on,I certainly did... particular in "the" positions like black has castled kingside, played g6, and white gets in Qh6 and bishop/pawn on f6... the null-move can hide the resulting mate...
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