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Subject: Algorithms for solving helpmates?

Author: Ian Osgood

Date: 10:43:09 01/07/00


Here is a little jaunt away from the same old alpha-beta/tablebase discussions:

There was a recent posting about a helpmate problem composed by Nunn which
stumped Karpov & Kasparov.  The problem: White has moved 1.e4.  Come up with a
line which results in 5.NxR checkmate.  You must determine whether this is
White's or Black's fifth move.

I have been thinking about how to solve this problem on a computer.  Since it is
a help mate with a very specific end condition, I would think a standard
alpha-beta search with a positional eval wouldn't work.  First of all, the eval
or search should detect the end condition at the appropriate plies.  Second, the
search should be full width, or prune based on problem specific info (for
instance, can a knight reach the king to deliver the mate on time).  I would
think a hash table would help to speed up any full width search.  Since we are
searching for a specific condition, perhaps a different search method such as
proof-number search would be more appropriate.

Does anyone have any experience writing helpmate solvers?  Anyone have any other
ideas about solving Nunn's problem?  Also, I am looking for public source code
for Proof-Number searching.

Thanks,

IanO




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