Author: Robert Hyatt
Date: 09:46:40 01/13/05
Go up one level in this thread
On January 12, 2005 at 20:57:40, chandler yergin wrote: >On January 12, 2005 at 20:33:25, Dann Corbit wrote: > >>On January 12, 2005 at 20:25:24, Uri Blass wrote: >> >>>On January 12, 2005 at 19:56:25, Dann Corbit wrote: >>> >>>>On January 12, 2005 at 19:37:29, Steve Maughan wrote: >>>> >>>>>Dann, >>>>> >>>>>>Things that seem impossible quickly become possible. >>>>> >>>>>I recon about 300 years before a computer will solve chess. This assumes >>>>> >>>>>1) 10^120 possible positions >>>> >>>>This is far, far too large. Chess positions have been encoded in 162 bits, >>>>which puts an absolute upper limit at 10^58 (and it is probably much less than >>>>that). >>>> >>>>>2) Alpha-beta cutting this down to 10^60 sensible positions >>>> >>>>The incorrect first assumption renders this and all following assumtions as >>>>moot. >>> >>>The second assumption is also not correct. >>> >>>By the same logic alphabeta can cut less than 2^30 positions in KRB vs KR to >>>2^15 positions but it does not happen and solving some KRB vs KR position with >>>no KRB vs KR tablebases is not something that you need 2^15 nodes for it. >> >>No. The second assumption would be true if the first was true. This was >>formally PROVEN by Donald Knuth. In a perfectly ordered alpha-beta solution >>tree, the number of nodes is proportional to the square root of the nodes in the >>full tree. >> >>If there were 10^120 in the full tree, then about 10^60 would be in the solution >>tree. >> >>It can be less than that. > >It "Can't be LESS than that! > > But it cannot be more. > > >It Certainly CAN! > >In any TREE.. the TREE ONLY represents "What HAS Been PLayed." >REFUTE THAT! >Can't HUH? > >Give it up! this is going nowhere. DC is correct here, and the math is there to support him. AB gives a minimal tree size with perfect ordering. If you do perfect ordering, the AB tree will _not_ be larger than the usual estimate. If you use hashing, it can be even smaller since you can avoid searching duplicate sub-trees that normal alpha/beta would search... In the above context, the tree does not represent "what has been played", It represents everything that has or can possibly be played in this particular position and its successors. Time to move on...
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