Author: Jeremiah Penery
Date: 00:06:20 10/04/99
Go up one level in this thread
On October 03, 1999 at 16:31:38, leonid wrote: >On October 03, 1999 at 15:07:58, Ed Schröder wrote: > >>>Posted by leonid on October 03, 1999 at 08:26:51: >> >>>I am not sure what you want to say with "extention" but my trying was very >>>simple. The identical positions were tryed on Rebel and Hiacrs using same >>>computer. Number of plys demanded were the same and from boths games it was >>>asked to make search by "brute force". Rebel was incredebly speedy. How >>>raw speed is implemented in final game it is the next question to ask. But >>>potential of the game is on its raw speed anyway. >>> >>>To Rebel was said: >>>1) Brute force - on. >>>2) Hash table - put to zero. >>> >>>To Hiacrs was said: >>>1) Selectivity - put to zero. >>>2) Hash table - put to lowest value possible, to 1024k. >>> >>>So, it is true that Hiarcs did his search at brute force and he really a >>>looser? Great mystery for me. >>> >>>Thanks to everybody who will make this enigma vanish! >>>Leonid. >> >>The keyword to understand the topic = extensions. >> >>Chess programs do use all kind of extensions and all chess programs do >>it another way. Some programs do not emphasize on extensions other >>programs heavily use extensions. >> >>A common example of an extension is to extend the ply-depth with "1" in >>case the king is in check. Thus instead of searching 6 ply the remaining >>tree is searched for 7 plies. If there is another king-in-check case found >>the search is extended to 8 plies and so on. >> >>So you see a 6-ply search isn't a 6-ply search as a lot of variations in the >>tree are searched deeper. >> >>Some program will extend king-in-check cases even more. On some types >>of checking moves Rebel will extend 2 plies. Other programs have their >>own ways of doing things. The end result is that you can't compare programs >>based on ply-depth. >> >>Ed > >This explanation puzzle me. My impression was that "brute force" in given >number of plys deep should include nothing but number of plys asked. Every >other extra ply for every other extra reason is inappropriate. I can only >understand that in all games logic should go some extra plys (or extention) >if it like to do this but not when "brute force" is asked. To see >some extra ply in "brute force" search (even partially) is pious fraud. It sound >like find the mate in 5 moves but announce it as mate in four. >Brute force search in certain number of plys signify for me search for all >the possiblities that existe for given position but going only the number >of plys said to be performed. If "brute force" is what I see it to be, it says >more that every other aspect of the game about the general capability of the >chess game itself. > >Leonid. What you are describing is a pure minimax search. No program does this. If a program tries to search _every_ possibile move to a given depth, it will take a very long time for all but the lowest depths. It would be pointless. All (?) engines use alpha-beta of some kind, which does not allow searching of _every_ node in the tree. I've read in other posts that you're worried about the branching-factor. If you do this kind of search (pure minimax), EVERY program will have the SAME branching-factor. Also, I'm puzzled. Why are you so worried about the "brute-force" search? For writing a chess program, it has almost no relevance. What exactly are you trying to determine? If you could narrow it down a bit, perhaps someone would be able to help you more. :) Jeremiah
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