Author: Robert Hyatt
Date: 20:53:31 10/15/99
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On October 15, 1999 at 19:11:48, Ratko V Tomic wrote: >> IE alpha/beta alone reduces the effective branching factor >> from 38 to roughly sqrt(38) == 6. Null move can reduce this by 1/2. > >Does Crafty has really an effective branching factor of 3 in typical middle >games in the full width search? Also, what's your guess on the proportion of >junk searched in such case. For the sake of simplicity we could define "junk" >anything that is, say, 1/2 pawn worse than the root node value (it could be >the running value of PV for simpler test). Would the percentage of the non-junk >nodes (e.g. the nodes within 1/2 pawn from PV value) go exponentially to zero >with depth? (That was the original point of disagreement in this small >exchange.) yes, 3 is pretty typical, although it steadily drops as material comes off. as far as 'junk' I have no way of measuring that, since alpha/beta doesn't provide 'how bad' a move is compared to another, just 'better' or 'worse'. > >I think it would be interesting if you could find time to rig your development >Crafty with few counters and get the proportions of (non-)junk in relation to >depth and also possibly its dependence on the delta (such as 1/2 pawn) >separating the junk from the non-junk. the problem is junk vs non-junk. I use PVS, which means except for a few dozen nodes, all the rest are searched with a null window. So that it is impossible to determine how much worse a move is than another...
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