The collection

Every essay — page 31

One idea per essay, ordered so that the earlier ones set up the later ones — but nothing here depends on being read in sequence.

Temperature

How much is at stake, measured. Thermographs, cooling, and why a player moves where the game is hottest.

Three populations, three answers. How often something is worth fighting over, measured on the catalogue of shapes, on the pieces a played game produces, and on the whole board those pieces make up.

One fight makes a board a fight

The rung below found 16 per cent of the components a played game produces to be hot, against 53 per cent of the catalogue they are drawn from, and predicted that the share of hot boards would be much larger. Taking the same play-outs and tallying at the board gives 32 per cent — twice the piece figure and not ten times it, because a Domineering board carries only 1.68 pieces and the hot ones cluster on the same boards.

6 figures · Cold
The ordering that does not order. Playing in the hottest component against playing by the larger of a component's two temperatures, over 220 boards. The proposed rule is exact far less often and its worst case is nine times as bad.

The quantity that does not order a board

The rung below found the players leaving an environment at the larger of a position's two temperatures, and proposed that a board should therefore be played in the order of that quantity. Over 220 boards of three components it plays exactly on 124 against playing-in-the-hottest's 196, loses 85 of the 97 disagreements, breaks Hotstrat's guarantee on six boards, and costs nine points on its worst one.

6 figures · Coupons
The rule that was supposed to lose. Five ordering rules on the same 220 boards. Playing where the temperature less the answer's is largest is exact more often than playing in the hottest component, which is what it was predicted, before the sweep, not to do.

A rule that beats the hottest

When promoting a component by its answer's temperature failed, the reverse was proposed — discount it instead — with a prediction, made before the sweep, that it would not beat playing in the hottest component. It does. It plays exactly on 201 of 220 three-component boards against 196, wins two thirds of the boards where the two disagree, keeps inside a guarantee proved for the other rule, and the gap widens as the board grows.

6 figures · Coupons
The board cools as it is played. Every position of a three by six Domineering board, grouped by how many dominoes are down. The share that are hot rises to four fifths and then falls to nothing.

The obstacle was the catalogue

The rung below could not measure the early game because its regions were too large for the catalogue, and asked for a bracket rather than a value. No bracket is needed: a twelve-square region evaluates in five milliseconds and an eighteen-square one in under a second. What was expensive was cataloguing every shape rather than sweeping the positions a board actually reaches — and the sweep says a board is hot four times in five three moves in, and cools when it breaks up.

6 figures · Cold
The third temperature is not consulted. Positions grouped by their two top temperatures, with the third temperatures they hold between them. The crossover is the same for every position in a group however far apart their third temperatures are.

The two numbers at the top

The rung below found the crossover of a sente fight to be its temperature less half its answer's, and said a proof would settle the depth question with it. The depth question is settled without the proof, by construction: group the positions by their two top temperatures and the crossover is single-valued on every group, however far apart the third temperature is — and the formula survives a fourth level of fight, which the rung below never reached.

6 figures · Sente
A plateau, not a point. The rule's score as the coefficient is varied on a fine grid. It is constant across the open unit interval and drops at exactly one.

The worst value in its own interval

The rung below scored a component by its temperature less its hottest answer's and asked what rate the answer should really be charged at. Every weight strictly between nought and one scores the same and beats the rung below's choice of one at every board size — because a ranking rule's score is a step function of its own coefficient, and one is exactly where two components tie.

6 figures · Coupons
The five hottest regions. Every eight-square Domineering region at the ceiling temperature, with which of the boards swept ever produces it.

Eight squares, and no hotter

The rung below found no Domineering position hotter than three halves on four boards and asked for the position that attains it. It is a region of eight squares, there are five of them up to symmetry, three are the hot core of an attaining board on every size swept — and the ceiling holds at nine and ten squares too, where the obvious extrapolation predicted seven quarters.

6 figures · Cold
Five premises, and the step. The claims an induction would need, with what checks each. The last row is the step and nothing here checks it.

The premises an induction would need

The rung below settled by a grouping test that a position's crossover depends on its own temperature and its answer's and on nothing below them, and asked for the induction. The four paragraphs are not written here; the checking they would rest on is. The law holds at five levels, survives translation, heating and cooling — and none of that is the step.

6 figures · Sente
Thirteen cells, thirteen scores. The rule scored in every cell of the unit interval on the designed pool, at three components.

A pool built to have an answer

The coefficient in the rule score a component by t − λa scored identically for every λ in the unit interval, because the rule reads an ordering and that pool's orderings changed at three places. A pool designed to have twelve crossings turns the interval into thirteen different rules, and all three board sizes agree on one cell: between a quarter and a third.

6 figures · Coupons
Three orders, one of them right. The holder's rank above the crossover under three different orderings of the options.

Which top is the top

The crossover law's proof rests on the walls above the crossover being governed by the top two options, and the check was never run. Run on 23,586 heights it holds exactly — but only when the options are ranked by mean value. Ranked by the temperatures the law is stated in, it fails on a fifth of them.

6 figures · Sente
One size further. The hottest Domineering region of each size, one size beyond what the rung below could reach.

The ceiling was a plateau

Three halves of a move looked like a ceiling on a Domineering region's temperature: it held at eight squares, at nine and at ten, and the rise that had been a quarter every two sizes stopped. At eleven squares four regions reach seven quarters — and they contain the hottest eight-square shapes and are hotter than them, so the extra material is not cold.

6 figures · Cold
The counts, beside what happened next. The hottest Domineering region of each size with the number of shapes attaining it, and whether the next size was hotter.

A description, and not a detector

The rung below noticed that the count of shapes attaining the hottest temperature grew across a plateau and collapsed at the step, and proposed it as a way to read a plateau off a single size. The growth is exact — five plateaus, no exception — and the rule is impossible: five orbits precede a rise at seven squares and no rise at eight.

6 figures · Cold
Two claims read as one. The proposed geometry separated into the claim the rung below established and the claim it needs but did not.

The four paragraphs prove something else

Three rungs earned the right to write the crossover law's proof as two straight walls meeting where the law says. The walls are straight — one of them everywhere, for a trivial reason, and the other only above the answer's own temperature. The crossover sits below that height, so the geometry holds nowhere the law is about, and where it does hold it proves the temperature instead.

6 figures · Sente
What a designed pool can say. Six statements about the coefficient, with which pool each rests on.

A second pool, designed differently

One designed pool put the rule's best coefficient between a quarter and a third, and all three board sizes agreed. A second pool, built by the identical greedy criterion from different material, has no cell that is best at every size — so the coefficient is a property of the pool and there is no number to find.

6 figures · Coupons
{2 | {1 | 0}}, added to itself. The value of n copies of one position, for each n, beside n times its mean and the smallest distance between the two. The mean value theorem says that distance stays bounded however many copies are piled up — and the bound is the position's temperature, which is what makes the temperature a second genuine measurement rather than a diagram-reading convenience.

The residues as a sequence

Four of the eight residue sequences never repeat, and a recurrence is not a description. There is a closed form and it is not for the game: the stops and the temperature of the n-th residue are periodic with period one, two or four on every sequence in the pool, while three of them produce a different game at every n.

5 figures · Temperature

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