Author: Robert Hyatt
Date: 11:15:05 07/06/04
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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... > >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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