Author: KarinsDad
Date: 20:43:09 10/16/99
Go up one level in this thread
On October 15, 1999 at 23:49:13, Robert Hyatt wrote: >On October 15, 1999 at 15:51:13, KarinsDad wrote: > >>On October 15, 1999 at 15:31:21, Robert Hyatt wrote: >> >>[snip] >>> >>> >>>Just remember that this is right in the heart of the 'chess loop'. Anything >>>you do here, you do once for every node in the tree, which means _often_. >>> >>>you could set up 7 linked lists and add moves to the end of the right list. >>>but when you analyze chess trees, you see why it doesn't work... because _so_ >>>many positions in the tree only search one move and exit. Why do all that >>>work? when 1/2 of the time it is absolutely wasted? >> >>Well, the simple answer is that you don't do it. >> >>The complex answer is that you could do it depending on the position and score. >> >>If you could predict with a high level of certainty whether you will get a >>cutoff or not, you could reduce the amount of branching by creating a sorted >>move order for those positions which should cutoff (note: I did not say that all >>moves had to be sorted) and by not creating a move order at all for those that >>should not cutoff. The problem boils down to coming up with a prediction >>technique that is relatively accurate. >> >>Any ideas on how to do that Robert? >> >>KarinsDad :) > > >It is partially doable. I did this pretty well in Cray Blitz, to predict where >to do a parallel 'split' for the parallel search stuff. You want to split at >ALL nodes (where all moves must be searched), not at a CUT node (where hopefully >only one move is searched, but sometimes 2-3-4 before the cutoff is found). > >But in general, it is difficult. And when you are changing your mind anywhere >in the tree, _all_ move ordering becomes backward as CUT nodes become ALL nodes >and vice-versa. And that blows you out of the water. That's something I have not yet experienced, so I would have never even considered it (even though you have said that this happens in the past). I'll keep an eye out for it. KarinsDad :)
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