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Subject: Re: overlapping tablebase lookup

Author: José de Jesús García Ruvalcaba

Date: 13:07:10 02/09/99

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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
>- 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

	But with IA-64 the processor will follow both branches simultaneously, there is
no chance for misprediction (only a waste of on the wrong branch).



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