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

Author: Robert Hyatt

Date: 20:13:26 07/21/04

Go up one level in this thread

On July 21, 2004 at 23:03:59, Eric Oldre wrote:

>On July 21, 2004 at 22:09:58, Robert Hyatt wrote:
>>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.
>Well not quite, I do!

You only have _one_ position at the root of the search.  How many moves can you
store in one position?  :)

More than one is a huge waste since "best" is all that counts in alpha/beta...

>Of course i hope to get that replaced in the future with something better. :)
>> 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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