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Subject: Re: Hitting the researchwall

Author: Robert Hyatt

Date: 06:20:52 08/24/01

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On August 24, 2001 at 06:30:39, Carmelo Calzerano wrote:

>On August 24, 2001 at 04:31:27, Tony Werten wrote:
>
>>My program searches for 4 minutes, gets to 14 ply (or whatever), makes a move,
>>takes a pondermove and starts pondering.
>>Now the first 12 ply are taken from the hashtable (<1 sec ) but it starts an
>>(almost) uninformed 13 ply search from which it is never going to return in the
>>allocated time, so it's just taking the best move it had from the previous
>>search, which is costing me plydepth. (and games )
>
>Why almost uninformed? You should have at least the PV from the previous
>searches, which combined with hash table information should be exactly
>what you need. Just get the 14 ply search PV, remove the first two moves
>from it (the move you actually made, and the move you are pondering on)
>and you'll have a 12 ply search PV to guide the 13 ply search.

If you get an EXACT hash hit on the first move, you won't have a PV.  If you
try to reconstruct the PV from the hash table, it might not be there due to
overwriting issues...

Internal iterative deepening is the solution to this problem.



>
>If the problem is that you get a one move PV due to the hash hit in the
>12 ply search, you could either start pondering directly from depth 13,
>or save/retrieve the PV to/from HT at the start/end of each search.
>HTH
>
>Regards,
>Carmelo



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