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Subject: Re: Returning PV from hash table

Author: David Rasmussen

Date: 15:50:29 01/15/03

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On January 15, 2003 at 18:38:38, Nathan Thom wrote:

>I just realised that my program LittleThought (in progress, hoping noone has yet
>used this name?) only stores the best move in the hash table, so when a hash hit
>occurs it cannot display the entire PV for that depth like everyone else's seems
>to.
>
>Do you all store the entire PV in the hash entry? or some other trick im
>missing?

No one stores the pv, it takes to much space.

In general, you can't always get the entire PV if you use hashing, and you do if
you want a serious program.

First of all, you can try to probe the hashtable for the position resulting from
the best move at ply 0 (the root) then if you get a best move for this resulting
position, this will be the next move of the pv and so forth. So you can probe
the hashtable to get the whole pv. It's a little more complicated than this in
practice, but you get the idea.

Secondly, it helps to store the pv in the hashtable after each iteration.

There are other tricks to try, too.

/David



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