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Approaching a life and death problem the right way
Path: GoodHabits · Prev: CallingOutAtari · Next: EstimatingTheScore Path: LifeAndDeath · Prev: EternalLife · Next: DonTBeGreedy
Keywords: Life & Death
You know when you are dealing with a life and death problem (tsumego) if you ask yourself either one of the following questions:
In order to answer these questions, it is a good habit to work systematically through all the possible moves that may work. A Kobayashi Koichi book or article may have recommended the following order: Isolate the group from the centerIf the group still has access to the center, it has a possibility to link up to friendly forces. Reduce the eye space of the group under attackThe classic example is a hane, hence the proverb that there is death in the hane. Look at the cutsIf there is a defect remaining in the group under attack, it may become a good deal easier to kill it if you manage to divide it into separate pieces. ("Divide and conquer".) PlacementsThe rationale is that the placement will mess up the shape of the group under attack. However if you start with this technique, the group under attack may still have options of running to the center or becoming a bigger group, i.e. a group with more space to create eyes. This is why you should first look at isolating it and reducing the eye space. --Stefan The Professional Approach vs the Amateur ApproachTo solve tsumego or real game problems, there is the professional approach as opposed to the amateur approach. Amateurs have more or less the following approach: Suppose we are to solve a tsumego:
In a real game, when our group is threatened, it goes something like this:
The professional approach is very different, or so I have been told. Suppose they are to solve a tsumego. They:
In a real game, when their group is threatened, they:
For one thing, professionals have exactly the same approach to tsumego as to real game situations. For another, a professional reads until he knows exactly what is going on (locally) and knows the meaning of each move in each of the branches. Finally, once the problem has been read out, a pro never returns to verify the status. He'll only continue to perform the third step (weighing local result/global position) regularly. We could try at least the professional approach in tsumego. If you continue to explore each possibility, even if you have found a solution, then you'll be surprised to find sequences that do the same thing as the one you already found, but with a better result in terms of points or aji. Moreover, exploring all moves, also the ones that don't work, does a great deal to your reading skills and your knowledge of shape. Charles Matthews In real life, there is even more involved. There is a proverb 'play kikashi before living' (they may not be sente later). And there is a possibly conflicting piece of advice: live in a way that improves the position on ko threats. It is even possible that you deliberately live in a way that allows seki later, for the sake of other aji. This came up in a famous consultation game where Kitani and Go Seigen made up one of the teams. I think that where the status of a group depends on some aji on the outside - which is often the case - one cannot really just read the position once and leave it. Sounds like hoping for the best. If the problem is to live and not just a capturing race, then a systematic way to solve life and death problems is to ask the following questions:
At each step of the process start at 1) and work your way down until the problem is solved. An example:
But there's not enough room to live. So we've exhausted the steps, and need to fix the first move. There is no other eye point, so we choose a spot that divides the inside area into two rooms.
White can try some squeeze plays as well, but rather quickly we found the important points to solve this problem. The hardest point in a life and death problem is when you need to expand your eye space. A few tricks are necessary for that.
The hard part about killing is seeing how to squeeze best. Sometimes it involves very clever sacrifice. More Discussion (moved from tsumego)Stefan: There are at least two approaches to tsumego. The first approach is to solve the problem more or less 'on sight'. Speed is a concern - you typically spend 20 seconds or less on the problem (even if that implies not completely reading it out), decide on the right move for the situation, and check your move versus the correct answer. The purpose of this kind of study is to internalise a lot of different situations and get them in your head as working knowledge. A bit like developing reflexes when you learn how to drive a car. I use this kind of study to get to know the basic shapes better and work them faster in games (tripod group, anyone?), as well as to increase my tesuji-spotting capability. The second approach is to take as much time as you need for a problem, but work it out systematically and don't look at the solution until you've convinced yourself you have completely read out all moves and countermoves (bonus points for working out the value of endgame sequences and how additional moves in the area influence the position). This takes a higher level of concentration. I use this kind of study to increase the accuracy and completeness of my reading (and frankly also to regain a bit the ability to focus, because the fast reflex-stuff makes me a tad sloppy in actual gameplay).
For the first approach I love taking a book a la Graded go problems for beginners and race from cover to cover. For the second approach I like the above mentioned Dieter: I think it is very important to continue searching the various plausible moves, even if you have found the solution to a tsumego. This way one learns to know the shape even better. Also, even if "one" move works, there might be a better move. This is one of the themes in the Kanazawa Tesuji Series. I invite everyone to add possible moves that I haven't included and the reason why they fail. DougRidgway: I've done a fair number of problems, including recently finished working through 1001LifeAndDeathProblems, and have some comments on how I do the tree search. Move order matters. It's much easier to prove that the right solution works against all opposition than it is to find it, so starting out with the right answer saves time. If you don't know where to start, the order suggested above is good (isolate, reduce, then cuts and placements), and straightforward moves before fancy ones is good too. After a failure, try the opponent's successful moves. The standard advice is to read each sequence once and only once, to completion, and then instantly recognize transpositions when they occur while reading future sequences. I'm not that strong, I find myself backtracking and retracing a lot. Terminal states matter. Terminal states are where you can stop reading, either because one side got two eyes, ran out of liberties (and no under the stones shape is left), or you recognize the shape and know the result. Static recognition saves work and increases accuracy, and I'm sure stronger players are much better at it than me. Know your ko assumptions. I.e., first assume that you will lose all kos -- this is optimism, you're assuming that you can live/kill without ko. Therefore, never read down a branch which involves you taking a ko, but the opponent always may. If you win, you have won without ko. If failure, then reverse the assumption, and try to win with ko. If you now succeed, then figure out what kind of ko it is, if a better ko is available, etc. Slavishly following this assumption fails when the final result involves a double ko, but these have to be recognized separately. When thinking about ko like this, local sequences never include ko threats or recaptures, which simplifies things considerably. This might be equivalent to assuming that first your opponent and then you are komaster. Most problems that I get wrong are due to misevaluating terminal states, usually by missing a shortage of liberties; getting confused visualizing the stones during reading or failing to consider a key move at all is much rarer. Path: GoodHabits · Prev: CallingOutAtari · Next: EstimatingTheScore Path: LifeAndDeath · Prev: EternalLife · Next: DonTBeGreedy This is a copy of the living page "Approaching a life and death problem the right way" at Sensei's Library. ![]() |