Author: Tom Kerrigan
Date: 12:39:05 01/08/00
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On January 08, 2000 at 12:41:13, Antonio Dieguez wrote: >On January 08, 2000 at 11:56:25, Dan Andersson wrote: > >>>"Extensions" are usually used to keep a program from running out of search >>>depth. My understanding was (probably very wrong) that extension are some kind >>>of addition search done for few next plys deep. If this is really so, how can >>>extension "keep program from running out of search depth"? > >that phrase traduced to spanish is not very clear I suppose you have the same >little problem, may be keep program from running out means keep program running >in ? > >>You said it yourself! By adding more depth. >> >>Regards DAn To jump the gun on Bruce a bit... If you are using some sort of recursive alpha-beta function, one of the arguments to that function is "depth". If you want to do a 10 ply search, you call the search function with depth = 10. For each successive call to search, depth is tyically decreased by 1. When it finally hits 0, it has "run out of search depth," so the quiescence search is called. An extension will increase the depth at a particular node. Let's say depth = 5 and you've reached a position where the side to move is in check. Typically, depth is increased to 6, so the position is searched 1 ply more than it would normally be. This is good because checks indicate that something is going on tactically in the position and you want extra accuracy when evaluating it. -Tom
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