Author: Gian-Carlo Pascutto
Date: 01:14:21 06/24/01
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On June 23, 2001 at 22:24:58, Robert Hyatt wrote: >My branching factor also remains fairly constant regardless of the depth. >It makes no sense to me that it would get smaller and smaller as you go >deeper. Because eventually it would have to go below 1 and the search >would actually get _faster_ as you go deeper. And that is fully nonsense. Actually, given the pruning methods we use now I think it is true that the branching factor gets smaller as we go deeper. Note that this does not mean that is HAS to go below 1. Take for example the nullmove in crafty. You do R=3 from depth 6 on, and R=2 before. That effectively means that as soon as we reach 6 ply in some lines we will have more efficient pruning. You can use R=4 from 16 ply on. Pruning again gets more efficient. If you throw some kind of extended futility pruning / limited razoring in the mix the effects get even more prounounced. You can easily see this in the tables at the end of Heinz's paper. They prune more as the depth increases. -- GCP
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