Author: Russell Reagan
Date: 23:45:02 11/15/03
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On November 16, 2003 at 01:29:52, Timothy J. Frohlick wrote: >To get to 14 ply with 11 to 12 good moves per ply would require a million >billion choices to be searched. I agree with Uri here. Taking into account the transposition table and iterative deepening, it is not unreasonable to assume an effective branching factor of 6, possibly 5 or even 4 (I'm not sure of the exact amount the transposition table helps out). 6 is surely a safe conservative assumption. 6^14 = 78,364,164,096 nodes At one billion nodes per second that's 78 seconds. Even at 7 million nps (which Crafty gets on a quad Opteron 1.8 GHz), it only takes 3 hours for a full 14 ply search. There are faster Opterons than what Eugene used to arrive at 7 Mnps, and 9Mnps could easily be reached with 2.2GHz quad Opteron. Then there are of course 8-way Opterons, and I've heard the Opteron will go as high as 2.6 GHz. A little rough math and I estimate that Crafty could go at around 18 Mnps on an 8-way Opteron at 2.6 GHz per cpu. That would mean a little over an hour for a full 14 ply search. If any non-pruning tricks could lower the branching factor to even 5, then we're talking 5 1/2 minutes to hit 14 ply. At a branching factor of 4, 15 seconds. If we consider the best programs that are getting close to a branching factor of 2 sometimes, that amounts to a 32 ply non-exhaustive search in a middlegame position in under 4 minutes. Wow! Maybe it won't be too long before chess is just like checkers, hitting endgame tablebases shortly after leaving book.
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