Author: Ed Schröder
Date: 01:30:44 09/26/04
Go up one level in this thread
On September 26, 2004 at 00:51:17, Sergei S. Markoff wrote:
>Some ideas on hash move extensions.
>The idea was invented independently by Shpeer, Rybinkin ("Mirage") and me. In
>most cases this is a good idea to extend TT moves to improve search stability.
>But what scheme will be best for doing it?
>
>In ST the method is a little curious.
>
>TT_extesion_amount=INCPLY/RootDepth (in plies).
>while(TT_extesion_amount*RootDepth<INCPLY) TT_extesion_amount++;
>
>Anyway it improves play of ST.
>
>I need your results to compare.
Since Rebel 12 I am using this:
in case of (2 consecutive best_move_from_hash_table
&& alpha < hash_table_score + margin)
then { extend with one ply in case this situation happens x times }
Notes:
. margin is currently set to 1.00
. x is currently set to 4, 8, 12, 16 etc.
. alpha in Pro Deo's philosophy could be beta in yours.
The background is simple, in case you have 2 consecutive
best_move_from_hash_table and the score is reasonable you most probably are in a
part of the tree with move sequences that make sense, thus extend.
One advantage of the algorithm is that not only the usual situations (checks,
re-captures etc.) are part of the extension but also the "normal" moves.
If you have Pro Deo then check the MISC_37 parameter and its sub-parameters for
the effects of the algorithm, the implications are simply huge.
[Pruning = MISC_37] * Hash table extension
[M37_VAL = 1.00] * margin is 1.00
[M37_count = 4] * in steps of 4
My best,
Ed
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