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Subject: Re:I found the answer

Author: rasjid chan

Date: 08:12:38 06/18/05

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Your "4 or 5 lines" for fail-soft is should be correct.
These lines are needed in FL to record the greatest FL score and we simply FL
with this irrespective of the bounds. Fail-high don't need any extra lines, we
simply return the score received from search() instead or returning beta.

When we hash FL/FH, I think we can safely hash the fail-soft score and not the
bounds and the theoretical advantage is straight-forward. So fail-soft is as
simple as it should be.

My earlier comments are actually for an attempt to have as good a hash-table
implementation as posssible by "preserving and passing down" an exact score.
It is posssible only with fail-soft.

When we eval() in QS and there is no move to search, we return eval-score.
we also return an int return_type = ex irrespective of the bounds. This ex
return_type may be preserved and passed downwards(I don't have the statistic
nor know the usefulness). So lower down when all moves are searched
and we have a FL, we may have a best score < alpha. An int best_type is also
kept which is done by applying reverse_type() to the return_type.
The best_type may be ex/ub/rep3. So we may end with FL below alpha(soft)
but we hash type as "exact" and not the usual "upper_bound" which is the default
if we don't pass down types.

If we have double bounds in hashing, then if we have depth=3,type=ex
and the hash table main bound is depth=4, type=UB/LB(not EX), we need not
discard hashing this search, but slot it into the secondary bound. The question
is how useful is all these work. I have found that the codes for passing
down "type" is rather straight-forward. As a comparison, implementing double
bounds in hashing is rather complicated.

Best Regards
Rasjid






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