Computer Chess Club Archives




Subject: Re: Can we use hash table at root?

Author: Tijs van Dam

Date: 02:48:20 02/01/00

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On January 31, 2000 at 21:38:39, Robert Hyatt wrote:

>On January 31, 2000 at 16:48:41, Tim wrote:
>>Crafty does not use(store and probe) hash table at root.
>>How about other programs?
>>Is there problem to use hash table at root?
>Suppose you look up the root position before you search a single move.  What
>do you get back?  A fail high?  etc.  There is really nothing useful to be
>gained by probing at ply=1, and exiting without searching a single move can
>cause some messy problems depending on how you write the code.  In my case,
>I didn't want to exit without searching as that confuses some bookkeeping that
>I do..

I use hash at root for my program GKJunior. But I won't let the root search
fail high or low on the hash, just use an exact value with its "best move" or
use a move with not enough draft to search first. This way, a best move will
always be found at ply=1. I have no problems and the code is not messy.

An advantage is that the search will continue very fast when the opponent makes
the same move as i was pondering, or to start pondering after making a move.
There is almost no delay, while crafty seems to take a few seconds to get to the
same PV as it had before the move was made.


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