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Subject: Re: First move beta cutoff percentage

Author: Scott Gasch

Date: 14:46:35 12/31/00

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Hi,

Sorry to followup my own note... but I've been experimenting with this in the
past day and wanted to share some observations.

First, I am trying out extended futility pruning as described by Heinz.  As you
might expect, when this is enabled the first move beta cutoff percentage drops
anywhere from 2%..10% in my tests.  This makes sense to me because I am pruning
away whole branches in which a fail high is very likely.

With this heuristic turned off my results are over 90% in most positions.

Interestingly this feature also costs my engine about 10k nps because I do not
prune checking moves but cannot tell if a move is checking until it is played.
This leads to a bunch of MakeMove ... UnmakeMove (and prune) which causes the
speed to suffer.  It's just a question of whether the smaller tree size is worth
the rate drop.

Scott




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