Author: Robert Hyatt
Date: 06:04:02 02/10/99
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On February 09, 1999 at 13:41:10, Jay Scott wrote: > >On February 07, 1999 at 18:30:17, Robert Hyatt wrote: > >>... when I do a probe, I _know_ I will get a result. So >>the search will definitely terminate here, with win/lose/draw scores. But I >>can't really go on until I know which... because of alpha/beta.... > >In principle you could go on nondeterministically, the same way modern >processors go on through a conditional branch before they've calculated >whether the branch is taken. > >For tablebase lookups, the drill would be: > >- start the lookup; it'll take a while >- predict the value you'll get back >- keep on searching as if the predicted value were correct this is the point. there is _no_ more searching here, period. Because if I probe, I am going to hit. And if I hit I won't search further. But I can't easily exit this node yet because I don't have the score. And with a depth-first search, trying to 'roll back' is essentially impossible, because the tree space is discarded as it is searched. And I don't see a good way to 'predict' the outcome anyway. The most common 'value' is DRAW. but predicting that would be bad... >- when the lookup finishes: > - if the prediction was good, you're set > - if the prediction was wrong, you have to roll back and start over: > - reset the search to that node > - zap any bad hash entries you made along the way > - undo any other changes... all of that would likely require a reverse tree search, which means waiting 2x as long before you can use the table value. > >I think this would be incredibly bug-prone. I wouldn't dare try it! >But if you can get the code correct, it would definitely be faster. > > Jay I'm not sure it would be 'faster' as "unrolling" a depth-first search means searching in the reverse direction, something i can't even do in the current version of crafty...
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