Author: Robert Hyatt
Date: 11:34:55 07/06/04
Go up one level in this thread
On July 06, 2004 at 14:27:52, Eric Oldre wrote: >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... >> >> >>> >>>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 > > >Thanks Robert, > >So when programs are printing out their "thinking" and reporting a depth of >"12/16", would that be indicating that the original depth of the search at the >root was 12, but that the pv was actually searched 16 plys? that I don't know. Crafty simply reports the iterative deepening iteration number, which is a sort of "minimum search depth" value. IE when you see the 14-> that means iteration 14 was finished and everything was searched that deep or deeper (ignoring null-move effects of course).. How others report the depth is a mystery to me. IE I have seen John Merlino post ChessMaster output where it said 1/14 and took 5 minutes to produce that output. What the "1" means is unknown to me. I don't like to try to compare search depths between different programs. Some forward-prune, some don't. Some are selective in other ways, some are not. IE if Crafty were to play ChessMaster with a fixed depth 1-ply search, I'd get killed. If we change that to a fixed depth 14 ply search, I'd win easily as chessmaster would lose on time within a couple of moves. Comparing search depths is sort of like comparing two automobiles by comparing their tachometer at 60 MPH. Only says how fast the engine is turning, not which is going faster or getting the best fuel economy... > >also, just wanted to say "good luck" with the remainder of WCCC. Crafty looks >like it's off to a strong start. Hopefully it will be able to keep it up. My goal was to play "solid chess". It seems to be delivering that, so I am happy regardless of the outcome. It can definitely play. And contrary to what "some" think it can be very dangerous and will have chances to win every game it plays... > >Eric
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.