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Fuzzy killers
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Evert Glebbeek



Joined: 21 Jan 2011
Posts: 2809
Location: NL

PostPost subject: Fuzzy killers    Posted: Tue May 14, 2013 7:52 pm Reply to topic Reply with quote

Inspired by the discussion in the history pruning thread, I did a quick experiment (no games though) with what I call "fuzzy killers". A fuzzy killer is a move that is not a killer move, but that has the same piece/to as a killer move (but a different from square, obviously). Another way may be "approximate killer". The idea is that if you can use piece/to for history (you don't are where the piece comes from, only where it's going), perhaps you can do something similar with killers.

I didn't have time to run any significant number of games, so I did an experiment with benchmark, the idea being that if it improves move ordering it probably improves the benchmark. As a matter of fact, it didn't - nodes searched went up by a few %. I also looked at a number of examples of fuzzy killers that turned up in the search and many of them look rather silly (so I decided to exclude moves with SEE<0 and not bother at all if the side to move is in check), but some looked quite reasonable.

The interesting thing is when I looked at statistics for number of beta cutoffs caused by "fuzzy killers" compared to the number of "fuzzy killers" that failed to produce a cut-off. To my surprise (because of the benchmark results) the number of fuzzy killers that produced a cutoff vastly outnumbered the number that didn't (I didn't save the numbers, but it was something like 1000 to 1). Unless I made a mistake somewhere (and I'll check that) this suggests to me that there is something to be gained from the idea, so I was wondering whether anyone has tried something similar?
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Subject Author Date/Time
Fuzzy killers Evert Glebbeek Tue May 14, 2013 7:52 pm
      Re: Fuzzy killers Don Dailey Tue May 14, 2013 8:05 pm
            Re: Fuzzy killers Evert Glebbeek Tue May 14, 2013 8:36 pm
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