Temperature
Temperature is a term imported from combinatorial game theory that indicates the urgency of making a play in a game. (For a definition, see Temperature (CGT).) It is typically more urgent[1] to make a play in a hotter game than in a cooler one. Temperature is related to several common Go terms.
While temperature in CGT is a property of a game, go players use the term to describe the whole board, or sometimes a local region of play. Generally, the temperature of the whole board, or simply, the temperature, corresponds to the size of the largest play (its miai value). As the game progresses, the temperature tends to drop. The local temperature corresponds to the size of the largest play in a region of the board. Generally speaking, a gote play lowers the local temperature and a sente play raises it, while if the local temperature stays the same, the play is ambiguous.
The ambient temperature refers to the temperature of the rest of the board besides the local region. In general it is the value of tenuki. As a rule it is time to make a local play when the ambient temperature drops below the local temperature. Sometimes the choice of a local play depends on the ambient temperature. A gote play, which lowers the local temperature, may be played with sente if its gote response is hotter than the ambient temperature. When both a local play by either player and its gote response are hotter than the ambient temperature, the play is double sente.
If two gote plays have the same size (in other words, if they are miai), then their combined temperature is lower than the local temperature of either one. If a play is the last one before a significant drop in the temperature of the whole board, it is tedomari. Tedomari is worth fighting for, as a rule.
Note: It is often useful to think of a game temperature that never rises during the game. Even if a hot battle erupts, as a rule it heats up a local region, while the ambient temperature remains the same.
-- Bill Spight
See also Temperature and Terminology Discussion.
[1] This has nothing to do with the go term, urgent play.
Kirk: I think it would be fascinating to have the local and global temperatures spelled out (estimates, at least) for a (small) game. It would start at the end, of course, where things can be calculated exactly, and move toward the beginning becoming somewhat vague no doubt as the endgame stage is left. Calculating the temperatures would point out likely errors in play. I am particularly interested in the value of non-territorial plays, and an exercise like this would help me to make some of these ideas more concrete. Has this already been done?
Bill: See http://www.msri.org/publications/video/index0.html and
http://www.msri.org/publications/books/Book42/files/spight.pdf for an analysis of the final stages of the Jiang-Rui Environmental Go Game. However, they do not discuss the size of non-territorial plays. Ishida does so in one of his books, but he seems to underestimate them. (His estimates are influenced by the traditional estimate of the first move as worth 10 points by miai counting. The size of komi strongly suggests that that is an underestimate.)
ilan: I note that temperature is never defined on this site, so this page and its variants are useless except for people who already know the definitions.
Bill: The second paragraph starts with the definition of temperature as adopted by go players, which is different from the CGT meaning, for which go players already have a term, miai value.
ilan: I looked up miai value, and it doesn't mention temperature anywhere. Also, the definition of miai value given there refers to moves, whereas temperature refers to positions.
Bill: True. Nonetheless, miai value in go corresponds to temperature in CGT. Go does not need temperature in the CGT sense, and most go players who use the term, temperature , do not do so in the CGT sense. And anyway, do you think it is appropriate to give the average go player either Conway's definition of CGT temperature in ONAG or my definition for extended thermography?
ilan: As it stands, it seems to me that these pages are essentially a discussion between you and Charles Matthews, and the material is incomprehensible to anyone else. At least, I haven't been able to understand any of it.
Jeff: I enjoy reading these pages. I understand much of it, but miss some. I'd ask Bill, Charles, and whoever else to please continue these discussions, though we certainly appreciate any effort to make them more clear!
Bill: Thanks, Ilan. That's helpful. I'll try to make things clearer. I think I'll also add a page for Temperature (CGT).
ilan: OK, and there is another thing which I don't quite get, which is your use of the word "urgent." As far as I can tell, the most urgent play is simply the correct move. By the way, I think this could also apply to "play urgent moves before big moves," but I suppose that there is an implicit meaning in "big move," as in "moves for which you can more easily see their value." I never never really understood temperature, which is why I was trying to real these pages. My impression was that it was a mathematical technique for reducing expressions such as {2 | -2} which seem like they should come from * = { | } because both players can move into final position with similar rewards.