Author: Tony Werten
Date: 23:05:18 07/06/04
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On July 06, 2004 at 14:15:05, Robert Hyatt wrote: >On July 06, 2004 at 14:05:24, Eric Oldre wrote: > >>On July 06, 2004 at 13:19:11, Robert Hyatt wrote: >>> >>>With fractional extensions, I believe it works best like this: >>> >>>extended=0; >>>if (something) extended+=ext1; >>>if (something_else) extended+=ext2; >>>... >>>etc. >>>... >>> >>>extended=Max(extended,one_ply); >>> >>>If you extend more than one ply you run the risk of reaching a position where >>>your search will be non-terminating. Your code runs the risk of not extending >>>enough. IE if your first extension is one ply and the last above is 1/2 ply, if >>>the 1/2 ply extension is triggered, that is all you will extend. Add 'em up and >>>limit them to 1 ply total should be better... >>> >> >>Robert, >>I have heard you mention before that you limit extending to one ply. What I've >>never been clear on is do you limit the extension to one ply for the entire >>search? or to extending only one ply per node? > >One ply per node. More than that and the depth can actually increase, >obviously, rather than getting smaller as you go deeper. 1 is potentially >dangerous but it is not very likely that you would extend 1 ply every ply you >search. > >Deep Blue used the rule "no more than two plies of extensions for every two >plies of search" which averages out like mine, but you could extend 2 plies at >ply=N if you extend 0 at ply=N-1. I tried it for a while but didn't like it as >well as what I do, as it tended to over-extend... Actually, I think it was a bit different. The used "never more than 2 ply" combined with "only extend on fail highs" wich basicly resulted in "never more than 2 ply in 2 moves" (special care was taken for pv nodes ) It's the "only extend on fh" that is typical about the the Deep Blue extensions ( not the 2 ply in 2 moves), and it limits the problem of overextending. Tony > > >> >>ie. if you are calling Search from the root with depth 10, is the maximun number >>of plys it will look ahead 11? or could it be more if you have criteria for an >>extension on multiply plys? > >In theory a 10 ply search could search to depth=infinity, but in practice >extending at _every_ ply is not likely. But I regularly see 30+ ply search PVs >from a 15 ply nominal search depth. > > > >> >>Eric
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