Misevaluation of cutting moves. Intransitivity in connections

[alain]

Cutting the tail of a dragon, and capturing it is valued nearly zero, (more precisely only the value of the move without the capture).

For Black at move 178 (last chance), M12 is valued 4.2, it is worth 40.0

Move at M12 threatens to attack M14
Move at M12 expands territory
Move at M12 connects N13 and J11
  M12:   5.00 (followup) - threatens to capture M14
  M12: 2.11 - change in territory
  M12:   5.00 - total followup value, added 0.00 as territorial followup
  M12: 2.32 - added due to followup (5.00) and reverse followup values (0.00)
  M12: -0.21 - shape (shape values +1.00(1) -2.00(1), shape factor 0.952)
Move generation values M12 to 4.21
3. M12 4.22

mv 179 M11 for White is valued 0.11 !

pattern 'CC43'+3 matched at M11
Move at M11 threatens to attack O11
Move at M11 cuts L13 and J11
Move at M11 strategically or tactically unsafe
  M11:   2.92 (followup) - threatens to capture O11
  M11: not a safe move
  M11: 0.01 - change in territory
  M11:   2.92 - total followup value, added 0.00 as territorial followup
  M11: 0.10 - cut/connect dame bonus
Move generation values M11 to 0.11

[alain]

mv 178 last chance to connect and prevent M11 cut (40 points)

[alain]

Using GoGui? too analyse this : W M11 is worth 28 points for the estimator.

estimate_score
= W+65.2 (upper bound: 68.8, lower: 61.6)

play w M11
= 

estimate_score
= W+93.0 (upper bound: 121.4, lower: 64.5)

[alain]

Comment from Nando: This is intransitivity example:

• A-B are connected
• B-C are connected
• A-C can be cut

WIP: Look at pattern CB3b in conn.c

[nando]

Yup, I was thinking of this:

Pattern CB3c

O!O
.*.
.OX

:8,B

c!a
.*.
.bX

;!oplay_disconnect(b,c) 
;&& !oplay_disconnect(c,a)
;&& xplay_connect(*,a,b) != WIN

Note: the oplay_disconnect() aren't expensive per se, since they will be verified sooner or later (during amalgamation in find_connections())

It could work alone, but maybe we additionally need something like following (which would also cover intransivities found by pattern CB2b)

Pattern CC403

O.O
..x        fragile double connection 
.O?

:8,-

dbc
.ax
.e?

;xcut(a) && xcut(b) && !xplay_disconnect(c,d) && !xplay_disconnect(d,e) && xplay_connect(a,c,e) != WIN

>amalgamate_most_valuable_helper(c,d,e);

As we said in our chat on KGS, a better solution would be to algorythmically find intransivities. I tried once and failed (just too expensive). Maybe you can come up with something... In the meantime, fixing this issue with a few patterns looks acceptable to me (provided they don't break anything and aren't too expensive, of course)

[nando]

I wish I could edit my previous comment...

I meant "... found by pattern CB3b"

[nando]

I tested my proposed patterns. First with CB3c alone:

Total nodes: 1693715088(+0.1%) 3342094(+0.2%) 12606306(+0.1%)

Breakage:

nando:23        PASS 0 [0]
kgs:220         FAIL N12 [T10]
kgs:340         PASS L4 [L4]

The PASS in nando:23 is simply ok.

N12 in kgs:220 is also rather big, but probably overvalued with the patch. The more important problem I see in this testcase is the fact that S9 is still seen as an OWL defense of T9.

L4 in kgs:340 is not bad, but the move only gets better valued because of the local connection issue. The engine still doesn't see the followup(s) (saving the stones on the right)

PS: Gunnar, does the tst() macro still work ok ?

[gunnar]

Replying to nando:

PS: Gunnar, does the tst() macro still work ok ?

Now it's repaired. Thanks for noticing.

[alain]

Another case : iliya-gorbyn-w134-h10.sgf. Just before W134 cut at H10:

Owl_attack E17: 0
owl_defend E17: WIN H10 (defense effective)

So E17 is said alive => no need to connect in H10! But once W has cut, black E17 is dead.
Some logic need to be improve, when owl_defense is connect, then the cut/connect move is worth a lot.

[alain]

Another example of intransitivity in connections:
 http://files.gokgs.com/games/2006/12/29/mamago-ggexp-2.sgf move 126+