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Subject: Re: Extensions and Futility Pruning

Author: James Robertson

Date: 09:35:50 05/05/99

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On May 05, 1999 at 02:18:11, Frank Schneider wrote:

>On May 04, 1999 at 20:51:00, James Robertson wrote:
>
>>Whenever my program makes an extension, say, at depth = 4 it finds it is in
>>check, it will not do any futility pruning/razoring for the rest of the branch.
>>I recently read that some programs will do pruning/razoring even if there is an
>>extension, unless it is at the current ply.
>Gromit is one of those programs. It uses part-ply-extensions and has lots of
>them, therefore there are extensions in many paths of the tree and switching
>off futilitypruning after an extension would result in a much larger tree.
>
>>Is this a better way to do things?
>>It seems like it would nullify some of the effects of extending, but it could
>>also save a tremendous amount of time too. What should I do?
>Test what works better for you.
>(I've never tried switching off pruning if an extension applied - I'll try
>that sometime).
>
>>
>>Thanks for any help,
>>James

I tried out both ways on the first 50 positions in WAC, and the version that did
not switch off pruning was about 20% faster. I made a mistake and ran the new
version at 5 seconds a move, while the old one at 10 seconds, and the new still
solved exactly as many as the old!

James
>
>Frank



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