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Subject: When There Seems To Be Little To Distinguish Between Some Moves by A-B

Author: fca

Date: 16:32:32 04/13/98


TRY TO MAKE LIFE HARD FOR THE OPPONENT!

Where several (2 or 3) moves keep shuffling about as being best-so-far
in various successive plies, they probably are almost
indistinguishable.... So (especially if the enemy is DNA-based) make the
final selection between the two *not* with the ply-dice (i.e. "at this
depth does this move displace the other one") but as follows:

1. Use a tree-audit perhaps on a sample basis.
2. Choose between the candidates *not* on the basis
of their backed-up evals but instead on how *few* lines were reasonably
successful against each...

So, if we are white, and + is good for us, and the candidate moves
(swapped around a few times) are say w1 and w2; if evals (obtained by
excursion) are:

w1 b11  --  +1.0
w1 b12  --  +1.1
w1 b13  --  +1.4
w1 b14  --  +1.2

and

w2 b21 -- +1.4
w2 b22 -- +0.98
w2 b23 -- +1.8

then I would choose w2 even though it minimaxes to 0.98 < 1, as the
bonus if black misses b22 is *big* ( i.e. 0.4 >> 0.02) (0.4 = b21 - b11;
0.02 = w1 - w2).  If getting
backed-up evals is too slow, sample the Black responses including
previous killer candidates etc.....

Yes I know 0.98 may not be an available number - hence I suggest the
trigger mechanism for us to go into this process is the swapping around
of candidates as search deepens.

As  comps get it wrong
too, so this should not only be an anti-human style, though kick-in
values could be set according to oppo type: if the perm brain has
correctly guessed a high proportion of oppo moves, it is probably a
comp)

Chinook did it yonks back when in its endgame databases and having to
distinguish between non-winning lines....  I propose extending it to
incomplete information datafields i.e. all of chess.

ICCAJ article (c10yrs back) " Pathology in Game Trees" is also
interesting....

Ideas?  Comments?  The process is time-cheap, and at worst it has done
nothing useful.  Shouldn;t have screwed up the hash table either....

Kind regards

fca

PS: And I can't find a trace of this in crafty - I looked :-)



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