Author: Robert Hyatt
Date: 16:51:16 04/20/04
Go up one level in this thread
On April 20, 2004 at 15:02:23, Uri Blass wrote: >On April 20, 2004 at 13:37:53, Robert Hyatt wrote: > >>On April 20, 2004 at 13:01:57, Dieter Buerssner wrote: >> >>>On April 20, 2004 at 12:52:47, Robert Hyatt wrote: >>> >>>>On April 20, 2004 at 11:50:29, Dieter Buerssner wrote: >>>> >>>>>On April 20, 2004 at 06:10:05, Omid David Tabibi wrote: >>>>> >>>>>>In his article "PEASANT: An endgame program for kings and pawns", Newborn >>>>>>writes: "Position 70 would require a 30-ply search (25,000 hours)" >>>>> >>>>>I did the experiment. A search without transposition tables, without >>>>>pruning/extensions and with material only eval (I forgot, if I used qsearch or >>>>>not). A pawn capture was found at depth 26 (after 8 hours, IIRC). >>>> >>>>I assume you mean depth=26, not ply=26? IE white wins the pawn and I had >>>>thought that this happens on ply=27, which means the first ply of q-search. >>> >>>Correct. Also, I used a qsearch in that experiment. >>> >>>>I will try to run this myself as it would be nice to know exactly how deep this >>>>is precisely, verified by multiple programs... >>>> >>>> >>>>> With hash, it >>>>>is almost guaranteed, that you find it at lower depth. Every second ply, you >>>>>will have to search all moves, and many inferior moves will be refuted by seeing >>>>>the pawn capture earlier. These refutations will be in the HT, and will be >>>>>grabbed in the other more decent lines, to find the solution at lower depth. >>>>> >>>>>For my engine, even 1000 entries in the HT is enough, to solve the problem in >>>>>practically no time. >>>> >>>>Theoretically if you search a perfectly ordered tree, the hash table should not >>>>let you solve it at a shallower than normal depth, although it should cut the >>>>time dramatically as we all see... >>> >>>I don't agree here. See my argument, that every second ply, you have to search >>>all moves, and that this will help you, to find abbrevations (especially, or >>>perhaps only, when using fail soft search). >> >>If you search a perfectly ordered tree this can not possibly happen. The first >>thing you search is the path toward the win. Other sub-trees have not yet been >>searched and they can't influence the score. > >If you use iterative deepening then it is possible that they were searched in >previous iteration so this argument does not convince me. > >Uri That is always possible. It is easy to test however, by just starting at some point rather than at iteration 1.
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