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Subject: Re: A move to search 2nd... Keep in the trans table?

Author: Robert Hyatt

Date: 19:09:58 07/21/04

Go up one level in this thread

On July 21, 2004 at 16:55:07, Eric Oldre wrote:

>lets say you are searching a position with iterative deepening.
>at depths 3,4,5 it finds a best move of Qd3. then at depth 6
>the best move changes to c4.
>When you start searching to depth 7, you clearly would want the
>first move you search to be c4, and this shouldn't be a problem
>if your transposition tables are working right. Since the best
>move should be stored in it.
>however, a good move to try 2nd would be Qd3, but your transposition
>tables aren't going to let you know that, at least not in the implementations
>that I have normally heard about.
>I was thinking that one way to overcome this would be to keep 2 "best" moves
>in the trans table. one to try first, and one that was a best move, before
>being replaced by a deeper search.
>Are other people doing this? or have you discovered that the cost is greater
>than the benefit?

Nobody uses the transposition table to order the moves at ply=1.  Much easier is
to just generate the ply=1 move list before you start the search, and as you
find a new best move, move it to the top of the list, pushing others down 1
slot.  This makes you search the best move from the previous iteration first,
then the next-best move from the previous iteration second, etc...

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