On Apr 28, 12:51 pm, raylopez99 wrote:
On Apr 27, 2:49 pm, "Inconnux" wrote:

Then you conceed my point and indeed the point of Crafty rating chess
players.

OK, now if I used Crafty for analysis of Fritz or Rybka games, it would
certainly not agree and would often call their moves 'errors' even though
they are FAR stronger than crafty.

In particular it will fail to spot moves where short to medium term
material gain is obtained at the expense of a losing long term
positional disadvantage that only shows up well beyond its terminal
node search horizon. The commercial programs with more aggressive
pruning and the largest range of positional heuristics at the moment
have the edge. And even then it is probably safer to use an ensemble
of the strongest programs guided by an independent GM to try and
analyse top players games for "perfection" meaningfully. All of the
engines have blind spots in certain positions.

To properly analyze the world champions
you would need to use a program that is atleast equal in strength to
these champions. Crippled Crafty just doesn't cut it... now if they
used Rybka for analysis I wouldn't have any problem
with the study.

J.Lohner

Not true at all. Crafty could easily tell you which programs far
stronger than itself played the most perfect chess. This is not
debatable.

Not necessarily. It might take Crafty an interminably long time to
spot that a certain capture leads to a situation where a pawn will
promote 30 or more ply into the future. Whereas an engine with more
sophisticated pruning and a heuristic for detecting "pawn can run"
patterns might see the ultimate outcome with a less than 20ply search.
I use this only as an example (I think Crafty is somewhat smarter than
this).

And I am not being rude about Crafty here. It does a lot better at
blocked pawn positions than Fritz8 which takes fully 15 minutes on top
end PC hardware to see into the classic puzzle quoted in Roger
Penroses book the "Emperors New Mind" as the sort of position
computers "will never understand". At the time he wrote the book in
1994 it was inconceivable that a program could search deeply enough or
understand that grabbing the rook and breaking up the protective pawn
barrier would lead to total disaster about 20 moves in the future.
Shredder10 now uses the position as a demo solved in 2s.

For instance, the winning program between two chess
programs playing each other by definition will produce at least one
less error than the losing program--and Crafty could, at some point,
appreciate this.

Apart from the fact that Crafty may not be able to see far enough into
the future to match the equivalent search depth of top commercial
engines or GMs there is another serious fault in your reasoning. The
only thing that you can say for certain when one program beats another
is that the losing side made a mistake that the winning program could
recognise and then exploit to its advantage. Or equivalently the
winning side saw something through selective extensions that the other
did not. Either side could have made many less than ideal moves up to
that point provided that the other was unable to extract any advantage
from it.

The only way you can get around your erroneous statement is to qualify
"properly" in "properly analyze". If you mean that it is better to
have an even stronger chess program than Crafty to better ("properly")
rate the champions, of course you're right and nobody would disagree
with you. But that doesn't mean Crafty's efforts are of no value.

Only that they are likely to be highly misleading in the situation
where the GM and/or a stronger program can see why the most obvious
strong move is not the best principle variation for gaining long term
advantage.

For detecting classic human blunders that can occur in any game any
decent chess engine will do. But if you seek to find the notional
"best" or "strongest" move in a given position you are first going to
have to define exactly what you mean by best or strongest. Some
positions may have several perfectly playable continuations that are
equivalent to within the noise on the evaluation function - even
though the program might still give them slightly different scores.

Playing against a much stronger player the continuation line most
likely to hold a draw has clear merit, whereas playing against a much
weaker player the one leading to a slightly risky quick win may be
perfectly OK.

Perhaps with a 'properly' written program you might have, in a close
tie, a switch between two players say tied for fifth place in the
pantheon of all-time champions

I am not convinced that scoring human GMs by how closely their play
resembles any particular named chess engine has merit. Perhaps ranking
them by percentage blunder rate might be meaningful though (and well
within the capability of any good chess engine). It is surprising how
effective blunder check can be even on GM level games given sufficient
time.

Regards,
Martin Brown