Generator

divide

A generator in the applied library, called 23 times across 3 essays. Below: what it draws at its defaults and at each mode an essay asks for, what it checks while drawing, and everywhere it is used.

divide is one function. Everything below came out of it during this build, at parameters taken from the essays rather than invented for this page — so a figure here is the same figure a reader meets in an essay, and if the generator changes, this page changes with it.

At its defaults

One cake, one halving cut at 4/9, and two measures of itA cake as a bar with two step valuations above and below it, the cutter's halving cut marked, and a table of both people's exact value of each piece.the cutter's measure, segment by segmentthe chooser's measure, segment by segment52530201553010552030cut at 4/9the left piecethe right piecethe cutterthe chooser5050130/3≈ 43.33170/3≈ 56.67the cutter's piecethe chooser's piecethe cutter's running total crosses 50 inside segment 3, 2/3 of the way through it, so the cut is at 4/9both pieces are worth exactly 50 to the cutter; the chooser takes the right one at 170/3 ≈ 56.67 andgains 20/3 ≈ 6.67 over half

show: "items"

Every allocation of 3 indivisible items, and not one of them envy-freeA value matrix for indivisible goods with the round-robin allocation shaded, the exhaustive counts of envy-free and EF1 allocations, and a control matrix on which envy-free allocations do exist.what each person would pay for each item, out of 100 for the setitem aitem bitem cperson 1person 2403525304525allocations: 8envy-free: 0up to one item: 4the control — the same search, on a matrix that has an answeritem aitem bitem cperson 1person 2503020203050allocations: 8envy-free: 2up to one item: 4round-robin pickingan envy-free allocationall 8 allocations of 3 items to 2 people were formed: 0 are envy-free, 4 are envy-free up to one itemround-robin picking, shaded, gives person 1 items a and c; person 2 item b — person 2 stopsenvying person 1 once item a is set asidethe control matrix underneath is searched by the same code and has 2 envy-free allocations, so anempty answer above is a finding rather than a broken search

show: "cutchoose"

One cake, one halving cut at 4/9, and two measures of itA cake as a bar with two step valuations above and below it, the cutter's halving cut marked, and a table of both people's exact value of each piece.the cutter's measure, segment by segmentthe chooser's measure, segment by segment52530201553010552030cut at 4/9the left piecethe right piecethe cutterthe chooser5050130/3≈ 43.33170/3≈ 56.67the cutter's piecethe chooser's piecethe cutter's running total crosses 50 inside segment 3, 2/3 of the way through it, so the cut is at 4/9both pieces are worth exactly 50 to the cutter; the chooser takes the right one at 170/3 ≈ 56.67 andgains 20/3 ≈ 6.67 over half

show: "trim"

Three people, a trimmed piece, and the nine comparisons that settle itThe four stages of the Selfridge–Conway division drawn along a cake, with the full three-by-three matrix of each person's value of each share.person 1 cuts three pieces of equal value to person 1piece 1piece 2piece 3person 2 trims the largest of them down to a tie with the secondthe trimming: 140/3 ≈ 46.67 to person 2person 3 chooses, then person 2, then person 1person 1person 3person 2person 3 cuts the trimming in three; person 2 chooses first, then person 1person 1person 2person 3the trimming, drawn at full widtheach person's value of each share — the diagonal is their ownperson 1's shareperson 2's shareperson 3's shareperson 1 valuesperson 2 valuesperson 3 values140/3≈ 46.6740/3≈ 13.33402040403540/3≈ 13.33155/3≈ 51.67own sharethe trimmingperson 1 cuts three pieces worth 100/3 each; person 2 trims 140/3 ≈ 46.67 off the largest, andperson 3 chooses firstthe verdict is the whole 3×3 matrix, not its diagonal: all nine comparisons hold, 1 of them as anexact tie

show: "moving"

A knife swept once, 4 proportional pieces, and 3 people who would rather have anotherThe successive cuts of a last-diminisher division along a cake, with each person's calling point marked and a matrix of every person's value of every piece.round 1 — person 2 calls first, at 1/42134round 2 — person 1 calls first, at 7/15134round 3 — person 3 calls first, at 27/4034the four pieces, and what each is worth to its ownerperson 125person 225person 325person 4117/2each person's value of each piece — the diagonal is their ownperson 1'sperson 2'sperson 3'sperson 4'sperson 1 valuesperson 2 valuesperson 3 valuesperson 4 values25202629312549/2≈ 24.5039/2≈ 19.502115253921/2≈ 10.5015/2≈ 7.5047/2≈ 23.50117/2≈ 58.50own piecea piece preferred to itthe knife sweeps once; person 2 calls at 1/4, person 1 calls at 7/15, person 3 calls at 27/40, andperson 4 takes what is leftevery own piece is worth at least 25 to its owner — the callers exactly — so the division isproportionalit is not envy-free: person 1 values person 3's piece at 26 against 25 for their own

What it checks while it draws

Collected by running the family and recording what it asserted, not written here. The count is how many separate times the claim was put to the test while these drawings were made.

Where it is called

Changing this generator changes every figure on this list. That is what makes the list worth publishing rather than keeping in a check script.

The whole library · What the figures prove