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Subject: passed pawn extension

Author: James Swafford

Date: 20:20:45 01/28/02



Does anybody do this?  I just implemented a passed pawn extension
that extends the depth by 1 if the move was a pawn move to the
sixth or seventh rank, and that pawn is not blocked by a pawn of
the opposite color.

The results are pretty disappointing.  It really blew up my search.
I decided to modify the implementation by saying only looking for
pawn pushes to the seventh rank, and it still can blow up pretty
bad.

Obviously most over the board positions would not trigger this
extension, but there are some that would blow up the search like
mad.

One thought I had is to use a fractional extension scheme.  That
may help, but I'd like to know if anybody else does this extension,
and what mechanisms they have in place to keep the search bloat
under control.

It's interesting to note that Bruce lists five different extensions
on his (excellent) web page; he hasn't actually written about any of
them yet, but passed pawn isn't even listed.  Hmm...

Any ideas or comments?

--
James



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