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Subject: Re: Hash and first Fail High

Author: Uri Blass

Date: 22:30:18 08/15/03

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On August 15, 2003 at 22:56:34, Robert Hyatt wrote:

>On August 14, 2003 at 15:27:06, Peter Fendrich wrote:
>
>>1FH = The ratio where the first generated move in the node is a Fail High.
>>
>>I experimented with removing the the hash table and became a bit surprised.
>>Normally I have about 1FH = 95-96%. When I removed the hash table that figure
>>raised to more like 1FH = 96-97% while the search depth, as expected, was
>>decreased.
>>
>>Increased 1FH when removing the hash table. Is this normal?
>
>Probably.  You increased the size of the tree.  And for the extra stuff you
>searched, you searched it pretty accurately.  But you _did_ search it, which
>slowed you down.  :)

Yes

If a program has good order of moves than the fact that hash tables are used for
pruning may reduce the % of 1FH

Maybe if hash tables are not used for pruning you can get more 1FH.

Another point is that it is impossible to compare between different programs by
% of fail high.

Suppose that I have a good rule of pruning of bad moves.
Using that rule may prevent the program to fail high after the bad moves because
the program prune them and even does not make them so the % of fail high is
going to be worse.

I also think that it is not clear what you do if null move produce fail high.
Do you consider it as 1FH?

Uri



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