I don't know how to argue against someone who disagrees, but if I see that I need a move, I would defend. Doing the opposite seems underhanded.
Re: Recent 9x9 game
Posted: Sun Sep 18, 2011 10:23 am
by HermanHiddema
In the actual game, komi was 6.5, so the issue does not arise
But apart from that, I wonder, how many of you spotted the ko?
Re: Recent 9x9 game
Posted: Sun Sep 18, 2011 11:21 am
by jts
$$W $$ +-------------------+ $$ | . . . . . . c b . | $$ | . . 2 X O a 0 9 d | $$ | X X 1 6 X 5 7 X . | $$ | X O X X 4 3 X . 8 | $$ | O O X O X X O X X | $$ | . O O O W X O O O | $$ | . . . . O O . . . | $$ | . . . . . . . . . | $$ | . . . . . . . . . | $$ +-------------------+
[go]$$W $$ +-------------------+ $$ | . . . . . . c b . | $$ | . . 2 X O a 0 9 d | $$ | X X 1 6 X 5 7 X . | $$ | X O X X 4 3 X . 8 | $$ | O O X O X X O X X | $$ | . O O O W X O O O | $$ | . . . . O O . . . | $$ | . . . . . . . . . | $$ | . . . . . . . . . | $$ +-------------------+[/go]
Or descends and the ko is on the other side. But this is an unwinnable double ko for B, right? Is there a better one?
Re: Recent 9x9 game
Posted: Mon Sep 19, 2011 1:40 am
by entropi
I spotted the weakness when I saw the position but did not see the ko.
But apart from that. This thread provides a potential for a nice discussion relating to the game's philosophy.
- DuskEagle-Helel camp thinks that black should pass and hope white does not see the tesuji.
- emeraldemon thinks that black should protect even if it means a .5 points loss.
I for myself am closer to emeraldemon. I don't think protecting and losing by 0.5 it is stupid or cowardly. It's a matter of how you approach the game.
I think I would neither pass, nor protect. I would resign immediately (unless I have the slightest doubt I miscounted or misread something). Currently in one of my games in DGS I just spotted a tesuji for my opponent that surely wins the game. Regardless of whether my opponent spots it or not, my next move will be a resign. If server allowed it, I would resign without waiting for my opponent's move.
I wonder what is the majorities opinion about that. Worth making a poll but too lazy right now
Re: Recent 9x9 game
Posted: Mon Sep 19, 2011 1:55 am
by HermanHiddema
jts wrote:
$$W $$ +-------------------+ $$ | . . . . . . c b . | $$ | . . 2 X O a 0 9 d | $$ | X X 1 6 X 5 7 X . | $$ | X O X X 4 3 X . 8 | $$ | O O X O X X O X X | $$ | . O O O W X O O O | $$ | . . . . O O . . . | $$ | . . . . . . . . . | $$ | . . . . . . . . . | $$ +-------------------+
[go]$$W $$ +-------------------+ $$ | . . . . . . c b . | $$ | . . 2 X O a 0 9 d | $$ | X X 1 6 X 5 7 X . | $$ | X O X X 4 3 X . 8 | $$ | O O X O X X O X X | $$ | . O O O W X O O O | $$ | . . . . O O . . . | $$ | . . . . . . . . . | $$ | . . . . . . . . . | $$ +-------------------+[/go]
Or descends and the ko is on the other side. But this is an unwinnable double ko for B, right? Is there a better one?
:b8: should just defend, then there is only a single ko. Of course, on this small board, black has no ko threats.
Re: Recent 9x9 game
Posted: Mon Sep 19, 2011 2:30 am
by ez4u
jts wrote:
$$W $$ +-------------------+ $$ | . . . . . . c b . | $$ | . . 2 X O a 0 9 d | $$ | X X 1 6 X 5 7 X . | $$ | X O X X 4 3 X . 8 | $$ | O O X O X X O X X | $$ | . O O O W X O O O | $$ | . . . . O O . . . | $$ | . . . . . . . . . | $$ | . . . . . . . . . | $$ +-------------------+
[go]$$W $$ +-------------------+ $$ | . . . . . . c b . | $$ | . . 2 X O a 0 9 d | $$ | X X 1 6 X 5 7 X . | $$ | X O X X 4 3 X . 8 | $$ | O O X O X X O X X | $$ | . O O O W X O O O | $$ | . . . . O O . . . | $$ | . . . . . . . . . | $$ | . . . . . . . . . | $$ +-------------------+[/go]
Or descends and the ko is on the other side. But this is an unwinnable double ko for B, right? Is there a better one?
In this case there is nothing. After , White captures with and Black has no ko threat.
$$Wc $$ +-------------------+ $$ | . . . . . . . . . | $$ | . . 2 X O . . . . | $$ | X X 1 6 X 5 7 X . | $$ | X O X X 4 3 X 9 8 | $$ | O O X O X X O X X | $$ | . O O O W X O O O | $$ | . . . . O O . . . | $$ | . . . . . . . . . | $$ | . . . . . . . . . | $$ +-------------------+
[go]$$Wc $$ +-------------------+ $$ | . . . . . . . . . | $$ | . . 2 X O . . . . | $$ | X X 1 6 X 5 7 X . | $$ | X O X X 4 3 X 9 8 | $$ | O O X O X X O X X | $$ | . O O O W X O O O | $$ | . . . . O O . . . | $$ | . . . . . . . . . | $$ | . . . . . . . . . | $$ +-------------------+[/go]
Herman's ko should be this
$$Wc $$ +-------------------+ $$ | . . . . . . . . . | $$ | . . 2 X O . 0 9 . | $$ | X X 1 6 X 5 7 X . | $$ | X O X X 4 3 X 8 . | $$ | O O X O X X O X X | $$ | . O O O W X O O O | $$ | . . . . O O . . . | $$ | . . . . . . . . . | $$ | . . . . . . . . . | $$ +-------------------+
[go]$$Wc $$ +-------------------+ $$ | . . . . . . . . . | $$ | . . 2 X O . 0 9 . | $$ | X X 1 6 X 5 7 X . | $$ | X O X X 4 3 X 8 . | $$ | O O X O X X O X X | $$ | . O O O W X O O O | $$ | . . . . O O . . . | $$ | . . . . . . . . . | $$ | . . . . . . . . . | $$ +-------------------+[/go]
However, after , Black has no ko threats. So correct play from the original position is for Black to exchange "a" for "b" to create a ko threat and then pass!?
$$Wcm11 $$ +-------------------+ $$ | . . . . . . 3 2 5 | $$ | . . X X O 1 X O 4 | $$ | X X . X X O O X . | $$ | X O X X X O X X . | $$ | O O X O X X O X X | $$ | . O O O O X O O O | $$ | . . . . O O a b . | $$ | . . . . . . . . . | $$ | . . . . . . . . . | $$ +-------------------+
[go]$$Wcm11 $$ +-------------------+ $$ | . . . . . . 3 2 5 | $$ | . . X X O 1 X O 4 | $$ | X X . X X O O X . | $$ | X O X X X O X X . | $$ | O O X O X X O X X | $$ | . O O O O X O O O | $$ | . . . . O O a b . | $$ | . . . . . . . . . | $$ | . . . . . . . . . | $$ +-------------------+[/go]
However! In this case White also has two ko threats starting with so White will end up winning the ko. Sheesh! See any errors here?
$$Wc $$ +-------------------+ $$ | . . . . . . O 4 1 | $$ | . 5 X X O O . O X | $$ | X X . X X O O X . | $$ | X O X X X O X X . | $$ | O O X O X X O X X | $$ | . O O O O X O O O | $$ | . . . . O O X O . | $$ | . . . . . . 3 2 . | $$ | . . . . . . . . . | $$ +-------------------+
[go]$$Wc $$ +-------------------+ $$ | . . . . . . O 4 1 | $$ | . 5 X X O O . O X | $$ | X X . X X O O X . | $$ | X O X X X O X X . | $$ | O O X O X X O X X | $$ | . O O O O X O O O | $$ | . . . . O O X O . | $$ | . . . . . . 3 2 . | $$ | . . . . . . . . . | $$ +-------------------+[/go]
Re: Recent 9x9 game
Posted: Mon Sep 19, 2011 4:07 am
by ez4u
Helel wrote:
ez4u wrote:However! In this case White also has two ko threats starting with so White will end up winning the ko. Sheesh! See any errors here?
Since my reading is pretty awful I'm in all likelihood imagining things, but what I had thought was that one of white's ko threats disappeared if black played b8 instead of c8...
Great idea! So that leaves us with the position below and White has no other ko threat after recaptures the ko. Black does not have to add a stone in the original position.
Oops! Still wrong. At this point White connects at "a". When Black plays "b", White recaptures the ko and Black has no threats left. White has no internal connection that helps the situation.
$$Wc , take ko $$ +-------------------+ $$ | . . . 5 b . O 4 1 | $$ | . X 6 X O O a O X | $$ | X X O X X O O X . | $$ | X O X X X O X X . | $$ | O O X O X X O X X | $$ | . O O O O X O O O | $$ | . . . . O O X O 8 | $$ | . . . . . . 3 2 9 | $$ | . . . . . . . . . | $$ +-------------------+
[go]$$Wc , take ko $$ +-------------------+ $$ | . . . 5 b . O 4 1 | $$ | . X 6 X O O a O X | $$ | X X O X X O O X . | $$ | X O X X X O X X . | $$ | O O X O X X O X X | $$ | . O O O O X O O O | $$ | . . . . O O X O 8 | $$ | . . . . . . 3 2 9 | $$ | . . . . . . . . . | $$ +-------------------+[/go]
Re: Recent 9x9 game
Posted: Mon Sep 19, 2011 4:58 am
by gaius
@ez4u:
In your first diagramme, you can swap the order of and . Then black cannot avoid the hopeless ko (except of course, if he sacrifices two stones, but that also loses the game ).
$$Wc $$ +-------------------+ $$ | . . . . . . . . . | $$ | . . 2 X O . . . . | $$ | X X 1 6 X 5 9 X . | $$ | X O X X 4 3 X 7 8 | $$ | O O X O X X O X X | $$ | . O O O W X O O O | $$ | . . . . O O . . . | $$ | . . . . . . . . . | $$ | . . . . . . . . . | $$ +-------------------+
[go]$$Wc $$ +-------------------+ $$ | . . . . . . . . . | $$ | . . 2 X O . . . . | $$ | X X 1 6 X 5 9 X . | $$ | X O X X 4 3 X 7 8 | $$ | O O X O X X O X X | $$ | . O O O W X O O O | $$ | . . . . O O . . . | $$ | . . . . . . . . . | $$ | . . . . . . . . . | $$ +-------------------+[/go]
Re: Recent 9x9 game
Posted: Mon Sep 19, 2011 5:39 am
by ez4u
gaius wrote:@ez4u:
In your first diagramme, you can swap the order of and . Then black cannot avoid the hopeless ko (except of course, if he sacrifices two stones, but that also loses the game ).
$$Wc $$ +-------------------+ $$ | . . . . . . . . . | $$ | . . 2 X O . . . . | $$ | X X 1 6 X 5 9 X . | $$ | X O X X 4 3 X 7 8 | $$ | O O X O X X O X X | $$ | . O O O W X O O O | $$ | . . . . O O . . . | $$ | . . . . . . . . . | $$ | . . . . . . . . . | $$ +-------------------+
[go]$$Wc $$ +-------------------+ $$ | . . . . . . . . . | $$ | . . 2 X O . . . . | $$ | X X 1 6 X 5 9 X . | $$ | X O X X 4 3 X 7 8 | $$ | O O X O X X O X X | $$ | . O O O W X O O O | $$ | . . . . O O . . . | $$ | . . . . . . . . . | $$ | . . . . . . . . . | $$ +-------------------+[/go]
Yes!!! So finally there is not even a glorious defeat, and Black has nothing to do but submit.
Re: Recent 9x9 game
Posted: Thu Sep 22, 2011 8:03 pm
by gonut
For an otherwise excellent problem, a minor issue is that under AGA or Chinese rules, Black wins.
From the original position, Black defends. Under AGA rules, White then gives Black a pass stone, whereupon Black has 27 points, White has 26 points before komi. Under Chinese rules, Black's defending move doesn't decrease Black's score, so Black again is ahead by 1 on the board before komi.
descends and the ko is on the other side. But this is an unwinnable double ko for B, right? Is there a better one?
, White captures with 
and Black has no ko threat.
, Black has no ko threats. So correct play from the original position is for Black to exchange "a" for "b" to create a ko threat and then pass!? 
so White will end up winning the ko. Sheesh! See any errors here?
recaptures the ko. Black does not have to add a stone in the original position. 
, 