Author: William Bryant
Date: 12:22:43 03/01/00
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On March 01, 2000 at 13:56:49, John Coffey wrote:
>The transposition table will tell us if a move is more desired than the other
>moves. So will iterative deepening and iterative iterative deepending. In both
>cases it seems necessary to sort the moves from most prefered to least prefered.
> What is the method for doing this? Is it just a standard sort routine?
>
>When doing move generation on a position that we haven't seen before, could
>we do things like sort captures to the top of the list, especially when a more
>valuable piece is being captured.
>
>John
<<Windows IE really stinks -- lets see if this will work this time>>
Move ordering can make a big difference in how your program plays.
How you do the ordering depends of the data structures of your program,
but the general theory goes as follows (but may vary from programmer to
programmer):
1. Search the Hash Table move (if there is one).
If you stuff the pv into the hash table then this will be the pv move
while you are following the pv.
2. If you are following the pv, and don't have a hash table move, this is
where internal iterative deepening helps
3. After searching the pv/hash table move, if you have not generated a cutoff,
then generate your captures and promotions.
Search winning captures first based on the expected gain in material either
by using a static exchange evaluator or by ordering using most
valuable target/least valuable attacker.
Search equal captures second.
4. After captures, search killer moves.
5. After captures and killers, generate the rest of the moves and search
the moves with the greatest history score first. Note this list should
also include loosing captures within this list.
The idea is to generate the moves as late in the cycle as possible to avoid
doing the work if you generate a cutoff sooner.
william
wbryant@ix.netcom.com
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