A little help?
I’m at 43 Kyu Problems - Semeai(mutual attack) The third board says, ‘Save the three black stones left alone in the corner!’ The board looks like this:
B_BW_
B_BWW
B_B_W
-BWW_
_B___
_B___
The only move that doesn’t end ‘Failed’ is B9. I don’t see any subsequent moves that don’t end in ‘Failed’. So after B9, where do I move, and why?
C5 is the winning move, not B9. I don’t know why B9 doesn’t show ‘Failed’ — coding error?
It looks like I was looking at the wrong board when I tried to code it in. :smack: Let me share a picture of the actual board:
That’s the one I’m having trouble with.
And that’s the one I was talking about too! (I noticed your wrong-position code only after I posted.)
As for why the webpage does not show ‘Failed’ after the failing B9 move, you might want to look at the website’s coding for that position: Play Go Online Game - Cosumi . (43K-3 for the third problem on the P43K page? ) Note that a different labeling is used: ‘B9’ is now ‘ba’; C5 is now ‘ce’.
NOTE: Clicking on link above is better than looking at this ‘CODE.’ The copy/paste destroyed useful indentation.
<data>
<name>43K-3-semeai</name>
<size>9</size>
<init>
B[ac]B[bc]B[cc]W[ad]W[bd]W[cd]W[cf]W[cg]B[dd]B[de]W[dc]W[ec]W[fc]W[db]W[ca]
</init>
<sequence>
<play pos="ce" res="be">
<play pos="bf" res="bg">
<play pos="ae" message="success@red"> </play>
<play pos="af" res="ag">
<play pos="ae" message="success@red"> </play>
<play pos="zz" res="ae" message="failed@blue"> </play>
</play>
<play pos="zz" res="af" message="failed@blue"> </play>
</play>
<play pos="zz" res="bf" message="failed@blue"> </play>
</play>
<play pos="cb" res="bb" message="failed@blue"> </play>
<play pos="ba" res="bb">
<play pos="ab" res="cb" message="failed@blue"> </play>
<play pos="cb" res="ab" message="failed@blue"> </play>
<play pos="zz" res="cb" message="failed@blue"> </play>
</play>
<play pos="be" res="ce" message="failed@blue"> </play>
<play pos="ae" res="ce" message="failed@blue"> </play>
<play pos="bf" res="ce" message="failed@blue"> </play>
<play pos="zz" res="cb" message="failed@blue"> </play>
</sequence>
</data>
The game tree shows no success after B9 (‘ba’) but does show White’s answers. Similarly after C5-B5-B4-B3 it doesn’t show ‘Success’ – it lets you pick either of two winning moves.
Perhaps failure to print ‘Failed’ does NOT mean you’ve not failed; it just wants to proceed for another move so you understand WHY the move failed.
@ Johnny L.A. — Did you even consider C5 in the target position, especially after I posted? This is not a hard move to find or understand.
I’ve given away my copy of Go for Beginners (which I recommend — it’s MUCH better than the Tutorial you linked to) but I can remember two things to quote:
(1) The book says you should first play several (100?) games of Go quickly, not even trying to think! They will be the most confusing games you’ll ever play, but after those games you’ll be ready to start thinking about your moves!
(2) The first chapter of the book reviews the rules while playing out a game on a 9x9 board. The very last sentence of the first chapter is quite tongue-in-cheek:
“Now you know how to play Go … almost.”
I remain convinced that it is much easier to become competent at Backgammon than Go. This assertion might make an interesting thread, but I won’t hijack this one.
It seems I come to this thread when I’m tired or distracted. When I read your post I inexplicably read C5 as C9. I’m glad I’m now on the same page!
Yes, I did try C5 even before you posted. I was trying so many iterations that I’d forgotten about it.
I finally figured it out. C5, B4, A5. I think my mindset was that I had to Save the three black stones left alone in the corner!, so I was thinking defensively instead of offensively.
OK, so I take the white stone by moving to E8. White can’t move to D8 because of Ko. But after the E2 and E1 moves, White can move to D8. Why? The top group of stones is separate from the bottom group of stones, so ISTM that White shouldn’t be able to move to D8 because it’s the same as if White went to D8 right after Black moved to E8. Why is it a legal move now and not then? The quoted text says it’s legal, but it doesn’t say why. 
Recapturing in ko is illegal ONLY IF the capture makes the position identical to what it was after your most recent previous move.
In the example, the position isn’t even the same: stones have been added at E1 and E2. But even if the position becomes identical to a previous position, the move is LEGAL unless the identical position was the IMMEDIATELY previous one.
Thus Go’s Rule of Ko is quite different from Chess’s Repetition of Moves Rule where, in principle, the repeated position might have arisen several moves before.
Because the Rule of Ko applies only in that specific situation, it is possible for repetition of positions to arise legally in Go. The simplest way this can happen is ‘Triple Ko.’ Suppose the Board has three Kos, call them A, B, C. White captures A, Black captures B, White captures C, Black Captures A, White Captures B, Black Captures C; lather, rinse, repeat!
When a Triple Ko (or similar repetition of positions) arises and neither player is willing to give way, the game is abandoned. It doesn’t score as a Tied Game; it’s like a Rained-out game in baseball. But this is extremely rare.
I think I see. Black moves to E8, White moves to E2, Black moves to E1. Since the previous move was not a repetition (E8, D8, E8…), White may now move to D8 and capture the stone Black put onto E8. If Black moves somewhere else, say B4, and White moves to A4, now Black is free to move onto E8. So as long as it’s not a ‘tennis match’, the stones in E8/D8 can be taken over and over.
Next problem: False eye (Second board, Try not to make a false eye’).
White cannot move to E5 or F4 because it would be surrounded by Black, so Black doesn’t need to move there. Black’s options are F6 or G3. If I move to G3, I get ‘success - you have two eyes clearly’. Any other move gets ‘failed - F4 has become a false eye.’ It won’t let me play it out to see what happens next. Would White move to F4, thus capturing the Black stones on E3, F3 and G4?
If Black makes the correct move to G3, can White move to F6 and then to E5 to capture the Black stones on D6 and E6? If White then moves to F4, would White capture all six stones in the middle group? Any others?
White could move to F4 (capturing only a single stone, not three) and then later play E5 to remove nine more stones. In practice White wouldn’t bother with these moves — the black stones would simply be removed as dead at the end of the game. (For White to actually play F4 would cost him a point and, more importantly in the mid-game, waste a tempo.)
No, E5 wouldn’t capture D6 and E6 because those stones are connected to the black chain at D5, D4 etc. (Instead, E5 would be an illegal suicide move.)
OK, let’s start from here. Black moves anywhere but G3. White moves to G3. Black moves somewhere else. If White moves to F4, it captures the Black on G4. If White then moves to E5 what happens? If Black has a ‘chain’ F3, E3, E4, D4, D5, D6, E6, then those stay Black, right? And if White then moves to F6, then all 8 Black stones (plus the one that was on G4) are captured?
I don’t remember what I read on scoring, and will have to re-read that section in my book. (At this stage, I’m just trying to learn how to play. Scoring comes later.) Can you remind me what makes stones ‘dead’?
Is that because the end of the ‘chain’ is G3, and there’s an ‘Exit’?
I strongly recommend you buy a beginner’s book like the one I recommended. And follow its advice and play several games at top speed against one of the on-line engines available, to get a feel for moves, life, death, scoring procedure, etc.
One “problem” is that there are minor rule variations which can— theoretically!— affect the final score and scoring procedure. As for which stones are alive and which are dead, in principle play should have gone on until both players agree on this, but under some Japanese rules, for example, there could be a post-game confirmation phase and arbitration by judges. Under some other rules, you would just keep playing.
White cannot play E5 at that point, it is illegal/suicide…white would have to play F6 first, then on his next turn he could legally play E5 and capture all the black stones.
The stones are dead if they have no hope of forming 2 eyes, or of “escaping” and connecting up with other black stones.
I have Go: A Complete Introduction to the Game by Cho Chikun. Daijoubu desu ka?
I’m not even sure it’s that simple: for example, a final position might have some stones in “seki” where there are not two eyes but nevertheless the other player will not capture them.
Well, I was just trying to give a simple answer in the context of the exercise for someone just learning the basics.
One difference (the most important difference?) between Japanese and Chinese rules, IIUC, is that arbitration is easier in Chinese — a player who thinks he might be able to kill an enemy group plays to kill it while opponent, in lieu of passing at his turn, must toss a stone on the board (or prisoner jar) whenever it’s his turn. IIUC, the final score will never differ by more than 1 point total among the different rule sets.
Another rule difference is “Superko” — In some rule sets, any repetition of position is prohibited (contrary to the detailed explanation I gave upthread). IIUC, the Superko rule is relaxed in Chinese and applies only to some repeated positions, and specifically not to Triple Ko.
Afore-mentioned Cho Chikun played at least three games in the 1970’s that were aborted by rare Triple Kos.
Cho, BTW, is one of the greatest players ever; he became a professional shodan before the age of 12. The fact that top go players (and chess players) usually start as very young prodigies would be a major bullet in my thesis that it is much easier to become competent at Backgammon than Go.
It’s a fine book (very likely ghost written ;))