Author: Robert Hyatt
Date: 19:21:05 09/25/00
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On September 25, 2000 at 16:12:34, Peter McKenzie wrote: >On September 25, 2000 at 13:47:03, Robert Hyatt wrote: > >>On September 25, 2000 at 11:41:18, David Rasmussen wrote: >> >>>Am I the only one who >>> >>>a) thinks that the kind of null move pruning that is done in Hyatt's Crafty is >>>the reverse of what Ernst Heinz concludes in his paper about ANMP >> >> >>I hope not. IE here is my code for that: >> >> null_depth=(depth > 6*INCPLY) ? 4*INCPLY : 3*INCPLY; >> >>Which says if the remaining depth is more than 6 plies, use R=3, while >>if the remaining depth is <= 6 plies, use R=2. >> >>The "6" is pretty arbitrary. I ran a lot of tests before choosing this >>number. Ernst found the same number totally independently of me, although I >>think we did use some "common tests" (ie WAC, etc) without knowing what the >>other was doing. > >Since I bought Ernst's book recently (only took 2 weeks to be delivered to New >Zealand) I've been thinking about implementing adaptive nullmove pruning. > >I noticed that Ernst uses a cutover of 8 (instead of 6) in the late endgame >(where both sides have 2 or less pieces). Do you do this in crafty? > >> no. I taper null-move off as pieces come off in an endgame, so that (for example) null-move is only tried near the tips (but not near the root to avoid some zug problems) when one side has only one piece of some kind. >> >> >>> >>>b) experiences better performance (less nodes, less time etc.) with Hyatt's >>>scheme than with Ernst's scheme. >>> >>>I.E. When I do >>> if (depth>6) >>> R=2; >>> else >>> R=3; >>>I get the best results. >>>Why? >> >> >>What is depth for you? Current ply? Or plies remaining? For me it is >>plies remaining before dropping into q-search, which means I am doing the >>same thing as Ernst, basically. Your code is the exact opposite of what we >>are doing, assuming 'depth' means plies remaining and not depth from root of >>the tree.
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