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Subject: Re: Failing low at the root

Author: Roberto Waldteufel

Date: 11:33:17 08/03/98

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Hi Bob,

Maybe I am misunderstanding what happened, but something sounds a little strange
here. When the search first finds that the pawn can't be held and fails low at
the root, it gives you an upper bound on the position that is less than the
value you previously used for beta by about the value of a pawn, so surely at
this point you re-adjust the search window at the root to take account of this,
so that when you re-search to depths 1,2 etc you do so with lower expectancy.
The positions you reach in the researches should mostly have bounds stored from
the search that failed low to start with, so I don't see why the search should
keep failing repeatedly unless you hit hash records from lower depths (before
the initial fail-low) and allow the lower depth re-searches to fail high and
override your upper bound from the orriginal fail high, but could you not easily
prevent this from happening by disabling the researching process until you had
reached your previous depth again? I would be surprised if Schaeffer is
recommending something as useless as you make it sound.

Best wishes,
Roberto



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