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| question about tsumego (GoChild) http://www.lifein19x19.com/viewtopic.php?f=15&t=5136 |
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| Author: | dohduhdah [ Sun Dec 11, 2011 8:05 am ] |
| Post subject: | question about tsumego (GoChild) |
Hi. Again, I have a question about a go problem: Dong-Dong grouping > (1) ~10k_6350 > (1) ~30k > (1) > 0062 Found at GoChild:http://gochild2009.appspot.com/?locale=en_US http://bayimg.com/PAlFNaAdf The solution given is for black to capture directly by playing at E7, but I was wondering if an alternate solution for black would be to capture indirectly by playing at F7 as shown in the screenshot. Is there any reason why one of these two solutions is to be preferred over the other? greetings and thanks in advance for any feedback, Niek |
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| Author: | Bill Spight [ Sun Dec 11, 2011 8:38 am ] |
| Post subject: | Re: question about tsumego (GoChild) |
Let me answer a simpler, but related question. In the given position all that is at stake are the two White stones and the single Black stone. Then the solid capture is better. However, there are situations where the gain from the indirect capture is greater than the local comparative loss of a little more than a point. Then the indirect capture would be preferable.  Keep looking for those alternative plays.
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| Author: | dohduhdah [ Sun Dec 11, 2011 9:10 am ] |
| Post subject: | Re: question about tsumego (GoChild) |
Ok, that seems to make sense. But generally speaking, is it usually better to capture directly in case there is also an alternative way to capture via snapback or is it equally likely that either the direct or indirect capture will be better depending on the context and possible continuations? Here are a few similar tsumego that involve the choice between a direct and indirect capture via snapback (where snapback capture is displayed in the screenshot): http://bayimg.com/GAljIAADf http://bayimg.com/iAljPaadF http://bayimg.com/jalJNaadF If I recall correctly it's usually better to capture directly if the alternative way to capture indirectly involves using a ladder. |
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| Author: | Bill Spight [ Sun Dec 11, 2011 10:47 am ] |
| Post subject: | Re: question about tsumego (GoChild) |
dohduhdah wrote: Ok, that seems to make sense. But generally speaking, is it usually better to capture directly in case there is also an alternative way to capture via snapback or is it equally likely that either the direct or indirect capture will be better depending on the context and possible continuations? Wrong question. You should always consider the alternatives, averages be damned. |
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| Author: | Toge [ Sun Dec 11, 2011 11:10 am ] |
| Post subject: | Re: question about tsumego (GoChild) |
dohduhdah wrote: - In first case, it's bad to capture with snapback as white can rescue her two stones in corner. In second case it is also wrong to capture with snapback, as black can place the group in atari. This can be used to help right side development or as a ko threat. Third case is the only really beneficial one. Exchange A5-A8 leaves white with weakness at B5. Tesuji like the snapback are only tools. When you internalize them, they help in planning your tactics. |
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| Author: | dohduhdah [ Sun Dec 11, 2011 11:19 am ] |
| Post subject: | Re: question about tsumego (GoChild) |
Bill Spight wrote: Wrong question. You should always consider the alternatives, averages be damned. But this is not always an option. For instance in a blitz game where there is no time to consider all possible continuations and you might be better off with general heuristics. |
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| Author: | jts [ Sun Dec 11, 2011 11:25 am ] |
| Post subject: | Re: question about tsumego (GoChild) |
dohduhdah wrote: If I recall correctly it's usually better to capture directly if the alternative way to capture indirectly involves using a ladder. What you say here is a little ambiguous. As a rule of thumb, if there are some stones you can capture, and it's vital that you capture them, and you have an option about how to capture them, your preference should be... dohduhdah wrote: http://bayimg.com/GAljIAADf This is probably a mistake. The direct capture at d7 relieves c10's shortage of liberties, and thereby cuts off b10; after e7, White can save the corner. However, if the situation on the rest of the board were such that cutting at either f6 or f8 were extremely valuable, damaging White's shape like this might make sense. dohduhdah wrote: http://bayimg.com/iAljPaadF Doesn't look like k10 accomplishes anything. Now W can choose between a free atari at k9 or favorable endgame around f12. dohduhdah wrote: http://bayimg.com/jalJNaadF This could be smart. The key thing to understand is that if Black just captures at a8 directly, she can later play a7 in sente. If White eventually has to take gote to play a7 himself, Black is equally happy. However, if the endgame moves around a7/a5 are already the biggest thing on the board, Black wants to play a7 immediately; whether she plays a7 or a8 the capture will be sente, but if she captures with a7 she gets an extra 4 points. |
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| Author: | Bill Spight [ Sun Dec 11, 2011 11:48 am ] |
| Post subject: | Re: question about tsumego (GoChild) |
dohduhdah wrote: Bill Spight wrote: Wrong question. You should always consider the alternatives, averages be damned. But this is not always an option. For instance in a blitz game where there is no time to consider all possible continuations and you might be better off with general heuristics. What is your goal? To play bad blitz? Or to play good go? You started out with some good questions. Keep that up. |
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| Author: | dohduhdah [ Sun Dec 11, 2011 12:22 pm ] |
| Post subject: | Re: question about tsumego (GoChild) |
Bill Spight wrote: dohduhdah wrote: Bill Spight wrote: Wrong question. You should always consider the alternatives, averages be damned. But this is not always an option. For instance in a blitz game where there is no time to consider all possible continuations and you might be better off with general heuristics. What is your goal? To play bad blitz? Or to play good go? You started out with some good questions. Keep that up. Well, basically my goal is to help improve gochild. Hence, I try to find alternative solutions when solving tsumego, but the problem I encounter is that it often seems that solutions are rather arbitrarily accepted or rejected. Hence I'm looking for arguments in favor of or against accepting or rejecting certain solutions, to improve overall consistency across the site. In some sections of the site, it might be ok to accept alternative suboptimal solutions for didactical purposes, but I think it's important to try and maintain some kind of consistency across various batches of exercises, so people can figure out the logic behind the exercises which implies whether or not they should pay attention to certain aspects (like finding the most optimal solution or simply learning about alternative ways to capture stones). -- Of the 4 examples I've referred to in this thread, only the last two accept both the direct and indirect capture as a solution at gochild, so my main concern at this point is whether or not there is a kind of logic behind this distinction between the former two and the latter two or whether it's more or less arbitrary. http://bayimg.com/PAlFNaAdf http://bayimg.com/GAljIAADf http://bayimg.com/iAljPaadF http://bayimg.com/jalJNaadF |
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| Author: | dohduhdah [ Mon Dec 12, 2011 10:39 am ] |
| Post subject: | Re: question about tsumego (GoChild) |
The last two tsumego were modified in response to my question about when an indirect capture via snapback might be an alternative for direct capture. Setting up a snapback is now only an alternative for direct capture in the last tsumego. |
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| Author: | Dusk Eagle [ Mon Dec 12, 2011 3:55 pm ] |
| Post subject: | Re: question about tsumego (GoChild) |
The difference between capturing directly and capturing via snapback can be subtle. Having said that, here's my take on the appropriate move in each case: Here I think it is better to capture at 'a' then to make the snapback at 'b'. For one, by making the snapback at 'b', black has left a bit of endgame for white by initiating the snapback sequence, followed by recapturing the black stone. Note that in some types of snapbacks this is not possible, but in this shape it is. But there is more to why I think it is better to capture solidly. Notice that if white plays the White 'a' - Black  - White 'a' sequence, it is a threat to cut off the three black stones on the right. This may not seem like such a big deal immediately, as black can capture the two marked white stones, but consider if white gets a move in the 'c' area at any point in the future - suddenly, black must respond to white's recapture at 'a', making the sequence sente for white. White will be able to improve his shape in the center in sente.Here, I would play the snapback shape at 'b' instead of 'a'. By playing 'b', you introduce an additional cutting points into white's shape. This one's subtle, but I would play 'a' as I see no reason to give white a free move at 'c'. If black's shape on the outside was better, I would take 'b' over 'a' for the endgame profit. However, black has shortage of liberty problems on the outside, so he should clear this issue up by capturing solidly with 'a'. To see what I mean by liberty problems, imagine white getting a stone at 'c'. Then moves like 'd' and 'e' work to cut off the lone black stone. This is the kind of aji black doesn't want to deal with, so capturing solidly is better. I'm not sure if this is what you were looking for, but I hope it helps somewhat .
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| Author: | dohduhdah [ Mon Dec 12, 2011 4:38 pm ] |
| Post subject: | Re: question about tsumego (GoChild) |
This is from the forum at GoChild ("Question correction records 5" thread), regarding the first three problems: http://bayimg.com/FalpKAAdf GoSharpLite created GoChild. |
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| Author: | shapenaji [ Mon Dec 12, 2011 7:44 pm ] |
| Post subject: | Re: question about tsumego (GoChild) |
dohduhdah wrote: This is from the forum at GoChild ("Question correction records 5" thread), regarding the first three problems: http://bayimg.com/FalpKAAdf GoSharpLite created GoChild. The analysis of the second problem on there is incorrect, the left diagram DOES look better, but that's because white has made one less move than in the right diagram. |
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| Author: | dohduhdah [ Tue Dec 13, 2011 3:26 am ] |
| Post subject: | Re: question about tsumego (GoChild) |
Dusk Eagle wrote: The difference between capturing directly and capturing via snapback can be subtle. Having said that, here's my take on the appropriate move in each case: Here, I would play the snapback shape at 'b' instead of 'a'. By playing 'b', you introduce an additional cutting points into white's shape. But is introducing those additional cuttingpoints worth allowing white to save its two stones in the corner (as mentioned by Toge and jts earlier in this thread)? |
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| Author: | Dusk Eagle [ Tue Dec 13, 2011 8:19 am ] |
| Post subject: | Re: question about tsumego (GoChild) |
Like this? Those two stones in the corner are not worth the horrible price white pays when black plays  . White loses a lot of potential on the top side and is cut off from the center. Black's power radiates into the center and onto the left side of the board. Even if black doesn't play , the fact that white can no longer atari at to get into the center and left side costs white a lot of power.
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| Author: | jts [ Tue Dec 13, 2011 10:27 am ] |
| Post subject: | Re: question about tsumego (GoChild) |
dohduhdah wrote: But is introducing those additional cuttingpoints worth allowing white to save its two stones in the corner (as mentioned by Toge and jts earlier in this thread)? Saving the corner is worth something like 10 points. I was wrong to say that SnapBack is wrong because it allows the corner to be saved , but I hope you understand the broader point... Which way you capture depends on what the rest of the board looks like. Most of the time slicing through white's position as DE demonstrates is worth more than 10 points; in fact, sometimes it's worth more than the original capture. On other boards, especially towards the end, it might be worth much less. Likewise, whether the difference between a solid whit wall and a slightly more massive wall with an easily defensible cutting point favors black or white depends on the board. On some boards it might be a great little endgame reduction; on yet other boards, it might destroy aji; on still other boards, it might create aji.
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| Author: | Dusk Eagle [ Tue Dec 13, 2011 10:52 am ] |
| Post subject: | Re: question about tsumego (GoChild) |
I'm not certain which one looks better for black to be honest. I prefered the second diagram for black to the first, but I'm far from confident in that answer. If the second diagram is better for white, then perhaps playing the snapback is incorrect here. |
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| Author: | dohduhdah [ Tue Dec 13, 2011 10:50 pm ] |
| Post subject: | Re: question about tsumego (GoChild) |
Dusk Eagle wrote: Like this? Those two stones in the corner are not worth the horrible price white pays when black plays . White loses a lot of potential on the top side and is cut off from the center. Black's power radiates into the center and onto the left side of the board. Even if black doesn't play , the fact that white can no longer atari at to get into the center and left side costs white a lot of power.Ok, but I reckon this depends on the overall position on the board where this tsumego occurs as a pattern. Would you agree it makes sense to allow both the direct and the indirect capture (via snapback) of the three stones as a solution of the tsumego or would you say your evaluation provides a compelling reason to exclude the direct capture as a solution? |
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| Author: | dohduhdah [ Tue Dec 13, 2011 10:58 pm ] |
| Post subject: | Re: question about tsumego (GoChild) |
jts wrote: dohduhdah wrote: But is introducing those additional cuttingpoints worth allowing white to save its two stones in the corner (as mentioned by Toge and jts earlier in this thread)? Saving the corner is worth something like 10 points. I was wrong to say that SnapBack is wrong because it allows the corner to be saved , but I hope you understand the broader point... Which way you capture depends on what the rest of the board looks like. Most of the time slicing through white's position as DE demonstrates is worth more than 10 points; in fact, sometimes it's worth more than the original capture. On other boards, especially towards the end, it might be worth much less. Likewise, whether the difference between a solid whit wall and a slightly more massive wall with an easily defensible cutting point favors black or white depends on the board. On some boards it might be a great little endgame reduction; on yet other boards, it might destroy aji; on still other boards, it might create aji.This is probably a problem with tsumego in general, that they usually present a rather isolated situation where its evaluation very much depends on the broader context where this pattern occurs. So that seems to imply one ought to include all solutions unless there is a really compelling reason to exclude certain solutions that is somewhat independent of the broader context. |
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| Author: | Dusk Eagle [ Tue Dec 13, 2011 11:07 pm ] |
| Post subject: | Re: question about tsumego (GoChild) |
It partially depends on what level of player the tsumego is aimed at, however, I think in general that only the best solution(s) should count. Lesser variations could perhaps be marked as such. In this example though I can't say with confidence which variation of the two below is better, if either. Thus, in this case I would count them both unless a professional or high-dan said one was better than the other. So, in my opinion, the guideline should be that if it's unclear which variation is better, count them both, but if one variation is clearly better, only count it (or mark the other variation as inferior). |
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