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[gnugo-devel] Evan's tests

From: bump
Subject: [gnugo-devel] Evan's tests
Date: Mon, 9 Sep 2002 09:24:54 -0700

Here are comments on some tests recently submitted by Evan.
Many of these positions are very complex. Evan may not be
aware of the use of | when alternate solutions are correct.
Some of the tests I don't understand and maybe Evan can give
more explanation.

(I) These are comments on Evan's 9x9 tests. The tests not
commented on seem valid.

Test 1: J2 does not owl attack J3, since if B answers
by connecting at J4 it is hard to see how W is going
to kill.

Test 3: F3 does not owl attack E3. If W defends normally at
F2 then C2 and H3 are miai and I'm reasonably sure that W is
alive. On the next move, however, W plays a bizarre defense
at E1, and --decide-dragon shows that W does not know how to
defend correctly. The real test is therefore at move 19.

(II) Comments on Evan's revision of the NNGS auto tests.

Test 7: this is difficult because it is a semeai problem.
P2 may work but it is certainly not the only move here. I
would play W J4 in this position to deprive B of an eye, and
L2, M2, perhaps even O2 may work. Since there are
alternative solutions, they must be given. But I don't think
this is really a good owl test, though it could be rewritten
as a semeai problem.

Test 9: I don't disagree with Evan's comment but about the
J7/J8 semeai. But also J4 would put W one move ahead. L10
is probably a better move, but giving it as the unique
answer to this owl defense test is wrong.

Test 11: As already explained L10 is not the unique
answer. L2 seems inferior to J4 because if B takes
J4 he gets 7 liberties. If W takes J4 B has effectively
only 4. Evan says "not sure how to look for both."
Use | (See owl.tst for examples.)

Test 12: I don't understand this test. Apparently Evan has
confirmed that GNU Go incorrectly believes that F9 connects
the stones at H10 and F7. The function owl_connection_defends,
which is called by the test, resides in owl.c and has the
following description:

/* Use the owl code to determine whether connecting the two dragons
 * (target1) and (target2) by playing at (move) results in a living
 * dragon. Should be called only when stackp==0.

It seems to me that calling this function is therefore MEANINGLESS if
(move) does not connect (target1) and (target2). So this test
seems wrong to me.

Test 13: This looks wrong to me. The question is whether at move
56, before B plays G10, H10 is critical. How can B capture it?
The game move at G10 can be answered at H10 and is very unclear
that B can capture it. It's also not a particularly important
stone. Generally let's not make owl tests for singleton stones
which are not cutting stones.

The remaining tests are unnumbered. I'll assume they are
numbered consecutively for the sake of discussion.

Test 14: GNU Go certainly understands on the basis of the
tactical code that F11 captures E10. This does not need to
be an owl test. Run gnugo -T on this position and notice
that the F11 stones are critical (red).

Test 15: similar comment. As a general point if the tactical
reading code understands the status of a dragon consisting
of a single string having four liberties or less the owl
code is not too relevant.

Test 16: good test.


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