Author: Tony Werten
Date: 23:45:08 02/23/03
Go up one level in this thread
On February 23, 2003 at 21:46:44, Robert Hyatt wrote: >On February 23, 2003 at 10:30:26, Tony Werten wrote: > >>On February 21, 2003 at 23:48:52, Robert Hyatt wrote: >> >>>On February 21, 2003 at 13:26:34, Alvaro Jose Povoa Cardoso wrote: >>> >>>>Could someone please define what "ALL node" is and axplain how do we process >>>>these type of nodes? >>>> >>>>Best regards, >>>>Alvaro Cardoso >>> >>>If you look at a perfectly ordered alpha/beta tree, after you search the first >>>branch at a node to establish alpha, you search the rest of the branches, and >>>at each successor you search only one node (the refutation move). But at the >>>next ply below that you have to search _all_ moves. This alternates down >>>through the tree. At "all" nodes, move ordering is totally irrelevant. At >>>successors to all nodes, you get "cut" nodes where you only need to search one >>>move, if you can search a good move first... >> >>If you're sure the other moves don't give a cutoff, why bother searching them at >>all ? >> >>Tony > > >I am not sure, as I said. 92% of the time the _first_ move causes a cutoff >if one occurs. That only leaves 8% for the rest. What is the probability >that the good captures, the hash move, the killer moves and a few history >moves won't cause a cutoff but a move left over will? Very low. But _not_ >zero. > >However, this is what forward pruning ideas are based on, and several programs >are using the idea to good effect, at the risk of overlooking something that >is obscure. I just haven't elected to take that "jump" yet, but it is on my >list of things to play with. You should I think. That 92% seems quite high. I'm happy with the branchingfactor of my program, but I come nowhere near 92%. If I would I would certainly try to "report fail low" after trying hashmove, captures, killers, 4 history, all checks and say 2 highest positional moves. Or the opposite. Report fail low at a cut node if the previous ones didn't give a cutoff. Might be safer because you'll end up researching the node (and if beta-alfa!=1 you won't skip) Tony
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