Generator

{5 | {4 | 0}} beside one other fight

{5 | {4 | 0}} beside one other fight
{5 | {4 | 0}} beside one other fight. A local position and a single switch, played out together at each of several ambient temperatures. The middle columns are what optimal play does: whether it opens the local fight, and whether it answers when the opponent opens it. The answer stops being forced at a temperature the local position alone does not name.

A local position and a single switch, played out together at each of several ambient temperatures. The middle columns are what optimal play does: whether it opens the local fight, and whether it answers when the opponent opens it. The answer stops being forced at a temperature the local position alone does not name.

11 essays call sente-crossover. The drawing above is what it returns with no arguments at all; every call below passes it something, because a placement that passes nothing draws whichever member of the family the generator happens to default to rather than the one its essay argues about.

The positions it draws

17 distinct positions, harvested by running this generator again at the options each essay passed it.

PositionWorth OutcomeDrawn in
{{12 | 2} | {1 | −3}} {{12 | 2} | {1 | −3}} L Double sente is not a property of the position
{{5 | 3} | {2 | −4}} {{5 | 3} | {2 | −4}} L Double sente is not a property of the position
{{6 | 2} | {1 | −3}} {{6 | 2} | {1 | −3}} L Double sente is not a property of the position
{{8 | 2} | {1 | −3}} {{8 | 2} | {1 | −3}} L Double sente is not a property of the position
{{4 | 2} | 0} {{4 | 2} | 0} N What a move nobody makes is worth
{{5 | 3} | {2 | −4}} {{5 | 3} | {2 | −4}} L Double sente is not a property of the position · What a move nobody makes is worth
{10 | {9 | 1}} {10 | {9 | 1}} L Sente is a fact about the rest of the board
{2 | {1 | 0}} {2 | {1 | 0}} L Sente is a fact about the rest of the board
{4 | {3 | 1}} {4 | {3 | 1}} L The answer that starts another fight
{5 | {4 | 0}} {5 | {4 | 0}} L A rule with no promise at all · Sente is a fact about the rest of the board · Two games in one environment · What a move nobody makes is worth
{6 | {2 | {1 | −9}}} {6 | {2 | {1 | −9}}} L What the halving is a function of
{6 | {4 | {3 | 1}}} {6 | {4 | {3 | 1}}} L The answer that starts another fight
{8 | {2 | −20}} {8 | {2 | −20}} L A pool built to punish greed
{8 | {4 | {3 | {2 | 0}}}} {8 | {4 | {3 | {2 | 0}}}} L A subtraction, not a factor
4 | 0 4 | 0 N Sente is a fact about the rest of the board
{5 | {4 | 0}} {5 | {4 | 0}} L What the halving is a function of
{6 | {4 | {3 | 1}}} {6 | {4 | {3 | 1}}} L What the halving is a function of

Where it is called

Changing this generator changes every one of these figures.

{5 | {4 | 0}} beside one other fight. A local position and a single switch, played out together at each of several ambient temperatures. The middle columns are what optimal play does: whether it opens the local fight, and whether it answers when the opponent opens it. The answer stops being forced at a temperature the local position alone does not name. Temperature

Sente is a fact about the rest of the board

A move that must be answered is called sente, and the word is used as though it described the local position. It does not. The same fight is answered while the rest of the board is quiet and ignored once it is busy, and the crossover — measured by solving the whole board at every temperature — sits at the follow-up's own temperature.

Is {{5 | 3} | {2 | −4}} double sente?. One local fight with a follow-up on each side, played out inside a sum with a switch whose temperature rises. The two middle columns are what optimal play does when each player opens the fight. Whether the opponent has to answer is settled by the ambient temperature and not by the shape, so the same position is double sente, sente for one player, and gote for both, at three different ambients. Temperature

Double sente is not a property of the position

A fight with a threat on each side is called double sente, as though the phrase named a shape. Swept against a rising ambient temperature, one such fight — { {5 | 3} | {2 | −4}} — is double sente up to an ambient of 1, sente for one player only from 3/2 to 3, and gote for both from 7/2, and the two band edges are the temperatures of the two follow-ups.

4 | 0 and {2 | {1 | 0}} in the same environment. Two positions and one coupon stack, solved as a single board. The rows are the line optimal play takes; the coupon on top when each position is first entered is compared with the coupon it was entered at when it had the environment to itself. The mean contributions still add and the entry coupons need not agree. Temperature

Two games in one environment

A coupon stack measures a position: play the whole board out and the coupon the players stop at is the temperature, the score is the mean. Put a second position beside the first and one of the two measurements stops working. Over 36 ordered pairs the contributions still add to the means every time, and the coupon a fight is entered at moves on 13 of them — without either position changing.

Four rules over 220 sums. Each rule plays every sum against an opponent evaluating exactly. Two of the rules come with a bound and two do not; the coldest rule is the control, and it violates the bound often enough to show that being inside it is a real constraint rather than a description of the pool. Temperature

A rule with no promise at all

Playing in a hottest component comes with a bound: never more than the largest single temperature below the mean of the board. Over 220 sums the bound holds 220 times — and so does the bound for a rule with nothing behind it, which scores exactly what perfect play scores on 205 sums against the hottest rule's 196. The control that shows the bound is doing work is the rule that plays the coldest component, which breaks it 74 times and loses up to eleven points.

The move that stops the other one. Six local fights, each placed beside an environment of known temperature. The last two columns are the band over which taking the local move beats spending the move outside, and the band over which the opponent's move in the same fight has to be answered. They are not the same band. Temperature

What a move nobody makes is worth

If Right's move in a fight has to be answered, then Left's move in the same fight prevents an exchange Right was going to get for nothing. That is a reverse sente, and pricing it is the awkward case: over sixty measurements the gain matches the local temperature once and the follow-up's swing twice, and the band over which the move is worth taking is not the band over which the move it reverses is sente.

Five rules over 120 sums built to punish greed. Each rule plays every sum against an opponent evaluating exactly, on a pool whose components are traps: a large immediate gain that hands the opponent a larger follow-up. The pool was built to punish the greedy rule and does not — that rule scores a move by the stop it leaves, and a stop already contains the follow-up. What the traps catch is the rule below it, which scores a move by the territory it takes and loses up to 16. Temperature

A pool built to punish greed

The rung below found a rule with no theorem behind it beating the rule with one, and predicted that a pool of deliberate traps would reverse the result. It does not. The traps miss, because the rule called greedy scores a move by the stop it leaves and a stop already contains the follow-up — and the rule the traps do catch, losing sixteen points where the guaranteed rule loses five, had to be written to make the point.

Where sente stops, by what the answer costs. The largest ambient temperature at which a local move is still answered, sorted by how deep the fight below the answer runs. When the answer ends the fight the crossover is the follow-up's temperature; when the answer starts another fight it is exactly half of it, and a third level does not halve it again. Temperature

The answer that starts another fight

A local move is answered while the ambient temperature stays below the follow-up's — and that rule, which this site has carried since the anchor opened, is exact only when the answer ends the fight. When the answer starts another one the crossover is exactly half the follow-up's temperature, on every position tested, and a third level of fight does not halve it again.

Two feet, and the one that halves the crossover. The thermographs of two follow-ups, drawn to the same scale. The first has a right wall that leans in from the axis and its move is answered up to the follow-up's full temperature; the second has a wall rising vertically first and its move is answered only to half of it. Temperature

What the halving is a function of

A move is answered while the board is cooler than the follow-up's temperature — or half of it, depending which of two classes the position is in, and the classes were stated in terms of forms. They are a feature of one wall: whether the follow-up's right wall rises straight up before it leans. Fifty-five positions, no exception, and the crossover becomes something a reader can see.

The crossover by depth. How far the ambient temperature can rise with the move still answered, by how deep the fight goes. Where the answer settles the fight it is the follow-up's temperature; deeper it is that less a half. Temperature

A subtraction, not a factor

The crossover factor was a half on fights whose answer starts another fight, measured on a pool with two three-deep positions in it. A pool built to be deep gives twenty, and the factor does not survive them: the crossover is the follow-up's temperature less a half on eighteen of the twenty, and a factor of a half agrees with that only where the temperature is one — which nearly every position in the earlier pool had.

Two clauses, one formula. The law split by which of the two temperatures is the smaller. When the answer is colder the correction is half of it; when it is hotter the correction saturates at half the fight's own temperature. Temperature

Half of the smaller temperature

The correction to the sente crossover has been priced twice — first as a factor of a half, then as a subtraction of a half — each time on a pool whose answers were all about the same size. Over 128 fights with answers from a number up to a temperature of six, the correction is half the answer's temperature, saturating at half the fight's own. Both earlier readings are regions of that one law.

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. Temperature

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.

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