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influence function
Path: AllAboutInfluence · Prev: ProfitThicknessOrFight · Next: KikashiAndInfluence Path: Speculation · Prev: · Next: BouzyMap
Difficulty: Advanced
Keywords: Strategy
I understand computer programs sometimes use an influence function to determine how much influence a given wall or other shape projects over the board. I was hoping to get some insight into what these look like. Are they a matter of assigning a value to the shape itself or computing numerical values for the influence of a shape at various parts of the board? For example, "the White wall creates 50 units of influence at the tengen, but only 15 at the side star region, and 5 near blacks thickness in the opposite corner" vs. "White's seven stone wall on the fourth line is worth the equivalent of 25 point of territory at this stage of the game". I think there might be room for both lines of thought. there is some merit in think of a stone as projecting influence like an electromagnetic field. The analogy is apt in that it helps one understand various concepts like: 1. In trying to reduce territorial frameworks it is often good to play on the junction line . One can overplay the junction line a bit if one's formation is stronger. See Attack and Defense by Ishida and Davies for an explanation. This makes excellent sense if one thinks of one's own stones and the opponent's as having opposite electric charges proportional to their strength. 2. Walls are very different from territorial frameworks. It is often a good concept to drive enemy groups right into one's wall whereas one would never wish to encourage the opponent to drive a spike through a framework. A wall can have a more significant effect on fights elsewhere than just a framework of friendly stones in that part of the board. This reminds me how, in the three dimensional world of physics, an electric field from a charged point or line will die off with distance, but a charged plane will cause a field which is constant in strength everywhere. Of course, with something like a capacitor plate there are edge effects, so the field will look constant in close-up and like an inverse square far away. This is somewhat similar to the effect of a wall in Go.
The field concept is not very useful when dealing with ladders, because these are a discrete tactical concept specific to Go, and the precise positioning of the stones matters. Generally, one should never try to substitute analogies or vague concepts, where reading out possibilities precisely is possible, but rather to guide one's intution. In accordance, another place where the field concept fails is when a wall has defects, or its life is in question. I don't believe I have ever had the experience of driving a group against a wall and then killing my own wall in the process (see WallDeath), but I tend to play very thickly and sometimes use walls for moyos instead. Nevertheless, I hear walls do die! Most importantly, the analogy fails in suggesting that an enemy wall should attract your stones! Neither side should play close to a wall, except to extend it or to forestall further extension of it. Otherwise, playing near a wall is inefficient for its owner and dangerous for the enemy. Can that be considered a "tactic" per se, slamming an enemy group into a wall and killing your wall in the process? That seems like an awfully large loss - 15 stones +? -- lavalyn To answer your question, I have heard of people killing their own wall and still winning, but I would not think of it as a tactic. I was submitting it as an example of a mistake which one should avoid, and one which isn't really covered by the idea of stones generating a "field" on influence. Moved here from influence by Charles Matthews Path: AllAboutInfluence · Prev: ProfitThicknessOrFight · Next: KikashiAndInfluence Path: Speculation · Prev: · Next: BouzyMap This is a copy of the living page "influence function" at Sensei's Library. ![]() |