Author: Robert Hyatt
Date: 17:37:29 07/30/99
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On July 30, 1999 at 18:01:15, Terry Ripple wrote: > I noticed that several of the top programs will initially do a brute force >followed by a selective search. For instance, when it shows a 9/30 in it`s >search, does this mean that it`s performing 9 ply brute force and then >performing up to 30 ply selective to complete its search for the position? I`am >using the Hiarcs 7.32 program! > > So, getting back to my question: If my program performs a 9 ply brute force >search, then this means it`s searching every possible move on the chess board to >complete a 9 ply brute force. This seems that it would need to search billions >of moves at times to complete such a task that comes from a brute force search. >This seems almost impossible with a home PC to do this kind of search with a >time control of 40/2hrs., but i know that it is doing this very task as this is >what it shows! > > How many moves or positions does it look at to perform a 9 ply brute force? The simple answer is this... alpha/beta makes the size of the 9-ply tree much smaller than you'd suspect. the typical branching factor is 38, but in the opening it is much smaller. To make this easy, however, assume it is 33, which means for a 9 ply search, you are thinking 33^9, while alpha/beta only searches sqrt(33^9). Since 33^2 is roughly 1000, and 33^4 is roughly 1 million, 33^4.5 is not as big as you might think...
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