Author: Ed Schröder
Date: 12:07:58 10/03/99
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>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
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