Author: Robert Hyatt
Date: 13:25:11 09/06/02
Go up one level in this thread
On September 06, 2002 at 15:47:24, Uri Blass wrote: >On September 06, 2002 at 14:42:02, Robert Hyatt wrote: > >>On September 06, 2002 at 13:33:29, Vincent Diepeveen wrote: >> >>>On September 05, 2002 at 14:06:08, Eugene Nalimov wrote: >>> >>>>Actually, often you don't want to search the objectively best move first. You >>>>want to search the move that will cause a beta cutoff and will result in a >>>>smallest subtree being searched. >>> >>>Not really, the best move is usually best, because usually the >>>problem of *a move* cutting off is shown next iteration by major >>>overhead. So at this iteration i a move could cutoff in very little >>>nodes, but if it next iteration fails low it obviously is a whole >>>subtree you researched. >> >> >>Would you _please_ think a bit before jumping in? Eugene's statement is a >>direct premise of any tree searching program based on alpha/beta. Do the >>least amount of work possible. Given a set of N moves that will produce a >>cutoff (fail high) and another set M that will not... If you search any moves >>in M first, you waste time and effort and slow down. If you search any move in >>N you get a cutoff and are done. How can it _not_ be best to pick the one that >>requires the least effort to fail high? Because once you fail high at a node, >>you are _finished_ there.. > >If this iteration is the last iteration you are right. >The point is that if the iteration is not the last iteration you may prefer >to have a move with bigger tree if it means that the tree for the same position >is smaller in later iterations. I disagree based on the "bird in the hand" proverb. I have a "bird in the hand"... I can cause a cutoff with minimal work. I have "two birds in the bush"... I will do a bit more work now and _might_ get a hash hit the next iteration that will save a little more. Serendipity is not a good neighbor in computer chess. Otherwise there are probably _lots_ of things you could do _now_ to make the next iteration go faster. If you can get there... > >I do not know if the best move is usually best and I guess that things are also >dependent in your pruning and extensions rules. > >You can also consider moves that force repetition as best if you get a cut off >by 1 node thanks to them. > >Uri
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