I analyzed these positions with Valkyria, and it has no problems
seeing what is happening in these positions. Also going back some
moves valkyria for example proposes Ws8 instead of Wp12 for move 218,
which clearly kills the black group and reduces it no eyes, and showes
that Valkyria does know what it is doing (it is not perfect but play
acceptable with a few seconds of thinking timew most of time).
My point here is just that playing strongly in one type of semeai does
not mean it will crush you. But you are right in that analyzing
positions like this can identify systematic weaknesse of programs. The
problem is that at least for how valkyria works there is not one
single fix, the problem is often that a special situation in the
playout has to be safely identified and a particulrly bad move need to
be pruned, or a deterministic response has to be made to some special
kind of threat. But these changes rarely apply to more than a small
proportion of the positions encountered in games. The main playing
strength come from efficient search in general, and the knowledge that
apply to common shapes rather than special tricky situations.
Nethertheless I discoverd a nice way of finding tricky situations
where evaluations goes very wrong.
I run long tests whith 50-500 playouts per move. I also allow Valkyria
to resign in these tests. This makes testing go faster and as side
effect one sometimes get very long games because the losing colour did
not understand it was losing.
So I play a 1000 such test games and look for unusually long games.
Often it was just a complicated even fight but sometimes one finds
some huge misevaluation to fix. Still fixing those things rarely give
a measurable boost to playing strength. But I hope they will add up in
the long run.
Best
Magnus
Quoting terry mcintyre <terrymcint...@yahoo.com>:
I haven't got a ladder example at the moment, but here's an instance
where Leela does not realize it is in terrible trouble.
I ( with my 8 kyu AGA rating) know with certainty by move 223 (T5)
that Black has captured a large white group. A stronger player could
read this out sooner than I. This fight is too big to lose for
either side; nothing else on the board matters. ( anyone? how early
is this outcome pre-ordained? )
Based on the results of its analysis mode, Leela does not recognize
the outcome of this semeai until the large white group in the bottom
right is down to two liberties.
The problem is even more stark in example2 -- similar board, black
has foolishly played one of his own liberties for illustrative
purposes. It is black's play, black has three liberties, white has
three. Black must take away a liberty from white to win the
capturing race, or make two eyes at T8. Black has only four playable
moves; any other choice fails.
Leela proposes - even after several minutes of analysis and a
million nodes - that Black should tennuki at H14. That would snatch
defeat from the jaws of certain victory; White would dive into T8
and win the race.
I started this thread with the contention that analysis mode can
help developers find problems, I hope this example explains why. My
theory is that if a program could reliably recognize the outcome of
such capturing races five or ten moves sooner, it could crush the
likes of me. :D
Terry McIntyre <terrymcint...@yahoo.com>
"Government is an association of men who do violence to the rest of us."
- Leo Tolstoy
________________________________
From: Michael Williams <michaelwilliam...@gmail.com>
To: computer-go <computer-go@computer-go.org>
Sent: Tuesday, April 21, 2009 1:57:54 PM
Subject: Re: [computer-go] Reply to Lukasz and Don + Roadmap 2020
Mention the program so that the author can either refute your claim
or fix the bug.
terry mcintyre wrote:
Is it reasonable to expect pro players to use 6-dan programs as a
tool for analysis? The pro players are markedly better - at a rough
guess, a pro player could give a 6 dan amateur human or program a
3 stone handicap.
On the other end of the scale, beginning players and mid kyu
players could indeed make good use of an analysis mode by a program
which is better than themselves.
Lastly, an analysis mode would be helpful to developers, methinks.
After winning a game, I like to back up a few moves and find out
when the program realized that it was behind. This often happens
several moves after the fatal blow has already been struck. I know
the feeling too well, when stronger players deftly skewer my group
and I only discover the problem five moves later. What do they know
that I don't? What do they know that the program doesn't?
We have a saying, you learn the most from reviewing games which you
have lost. An analysis mode can help developers to discover when
their pride and joy first begins to miss the target.
Lately, I have been playing quite a bit with a commercially
available program. An almost-ladder which has an extra liberty will
apparently be evaluated the same as a true ladder, and the program
can be tricked into trying to capture my ladder-like position.
This sort of predictable flaw might provide a clue to improve the
next version.
Terry McIntyre <terrymcint...@yahoo.com>
"Government is an association of men who do violence to the rest of us."
- Leo Tolstoy
------------------------------------------------------------------------
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--
Magnus Persson
Berlin, Germany
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