Author: John Coffey
Date: 10:25:12 09/21/98
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>So, roughly, alpha/beta reduces the branching factor from W to sqrt(W). >To drive it below that, requires unsafe tricks. IE null-move is one big >winner here, because some nodes are searched less deeply than others, which >can reduce the effective branching factor from sqrt(W) to something even >less, approximately 2.5-3.0, roughly, in Crafty... > > Let us assume that squrt(W) is in the 5 to 6 range, then in order to get the numbers down to 2.5 to 3 that we would have be eliminating half of all the moves on every branch of the tree. Seems to me that null-move won't even get you close to that, so it occurs to me that most of your speed up must be coming from hash-tables being used at every branch to get near perfect move ordering, thus improving the efficiency of the alpha-beta algorithm. Is this not so? By "near perfect move ordering" I mean that the best move is usually tried first. I am guessing that all the other moves would be close to random order. john coffey
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