Author: leonid
Date: 10:24:48 06/19/01
Go up one level in this thread
On June 19, 2001 at 13:17:16, Angrim wrote: >On June 18, 2001 at 19:49:50, leonid wrote: > >>On June 18, 2001 at 15:59:36, Heiner Marxen wrote: >> >>>On June 18, 2001 at 03:45:49, Angrim wrote: >>> >>>>On June 17, 2001 at 16:55:53, Heiner Marxen wrote: >>>> >>>>>So let me ask: what is the status of your code? May we look at it? >>>> >>>>My code is private, sorry. However I would be glad to answer >>>>questions about how pn^2 works. I have spent a fair amount of >>>>time on pn^2 since it is very handy for checking the safety of >>>>openning lines in suicide chess. I just had to plug in the >>>>rules of chess to get a chess mate solver. >>> >>>Thanks for your offer! >>>Next time when I try to understand or implement some sort of pn search, >>>I will remember it and email you. >>> >>>Heiner >> >>If somebody between you will explain to me, in genral term, what it is all about >>(pn search) will be very thankful. > >pn-search(proof number search) is a general purpose game tree proving >heuristic. I will try to explain it here briefly, but I think that the >thesis does a better job. > >Each node in a search tree is assigned a proof number and a disproof >number, such that the proof number is the number of leaf nodes of the >subtree which would need to be proven to prove the root of the subtree, >and the disproof number is the number which would need to be disproven >to disprove the root of the subtree. >At each iteration in the search, it expands a leaf node of the search >tree which would (if proven true) reduce the proof number of the root, and >which (if proven false) would reduce the disproof number. If the leaf >node is neither proven nor disproven, its proof and disproof numbers are >calculated, and propagated back through the tree, possibly increasing >the proof and/or disproof numbers at the root of the tree. > >When used for chess, a node is proven if the side to win delivers checkmate, >and disproven if they are mated. Draws are a pain in the neck, but can >generally be scored as having pn and dn of +infinity since a drawn >position can never be proven to win for either side. Alternately a >draw can be scored as a loss for the side that is trying to win, >which makes things a bit simpler but makes the values asymetric. > >>Cheers, >>Leonid. > >Angrim Thanks for explanation! Leonid.
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