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Subject: overlapping tablebase lookup

Author: Jay Scott

Date: 10:41:10 02/09/99

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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
- 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...

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



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