Computer Chess Club Archives




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

Author: Tijs van Dam

Date: 08:38:48 02/01/00

Go up one level in this thread

On February 01, 2000 at 09:30:05, Robert Hyatt wrote:

>>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.
>you just mentioned one messy detail.  "no fail high or low".  This means that
>for _every_ hash probe, you must be checking to see if you are at ply=1 before
>you do the fail high or fail low?  All for no benefit at all.

No, like Crafty I use a different funtion for the root search.

>>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.
>I do this differently.  If I complete a 12 ply search, and start to ponder,
>I ponder the 2nd move in the PV, I shift the PV two moves left to get rid of
>the move I made and the move i am pondering.  I then start the search at old
>depth-1 since I already have the PV from old depth-2 done...
I see, I hadn't thought of that. But then this has the same result as storing
and probing at root, because depth 1...depth-2 are found immediately. This makes
it easier to implement pondering / using the ponder result, because every search
can start at depth 1 without cost.

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