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Subject: Re: Questions to Dr. Ernst A. Heinz about move ordering

Author: Robert Hyatt

Date: 19:40:12 10/24/00

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On October 24, 2000 at 20:01:31, Pham Minh Tri wrote:

>Hi,
>
>In the book "Scalable Search in Computer Chess" you listed the move-ordering
>scheme as following:
>1. hashed move
>2. good capture moves
>3. killer moves
>4. history moves,
>5. statically pre-sorted remaining moves
>6. bad capture moves.
>
>My question are:
>1. How about pv move? Do you install them into hash table? If yes, what is
>benefit (I think if we keep separating pv and hashed moves, we will have more
>good moves for searching first).

I'm not Ernst, but think about your question.  Why would the hash table have
a "best move" that is _not_ the PV move?  The only problem is that the hash
table won't have a best move for every ply, because every other ply doesn't
have a "best move" at all in the context of alpha/beta.  The fix (for me) is
to simply "stuff" the PV into the hash table at the start of each iteration.





>2. How do you divide good and bad capture moves? Are the bad capture moves
>really "bad" therefore you listed them in the end (I mean they would be higher
>order)?
>3. Could you explain more details about statically pre-sorted remaining moves?
>Thank you in advance,
>Pham


Ernst uses MVV/LVA, which means the first capture he tries is the most valuable
piece that is being attacked by any of his pieces, and then he tries the least
valuable attacker for that piece.  Others of us use SEE (static exchange
evaluator) which is a bit more accurate, but costs a bit more computationally.



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