Go First Dice are a set of dice in which, when rolled together, each die has an equal chance of showing the highest number, the second highest number, and so on.[1][2]

The dice are intended for fairly deciding the order of play in, for example, a board game. The number on each side is unique among the set, so that no ties can be formed.

Properties

There are three properties of fairness, with increasing strength:[1]

  • Go-first-fair - Each player has an equal chance of rolling the highest number (going first).
  • Place-fair - When all the rolls are ranked in order, each player has an equal chance of receiving each rank.
  • Permutation-fair - Every possible ordering of players has an equal probability, which also insures it is "place-fair".

It is also desired that any subset of dice taken from the set and rolled together should also have the same properties, so they can be used for fewer players as well.

Configurations where all die have the same number of sides are presented here, but alternative configurations might instead choose mismatched dice to minimize the number of sides, or minimize the largest number of sides on a single die.

Optimal results have been proven by exhaustion for up to 4 dice.[1]

Configurations

Two players

The two player case is somewhat trivial. Two coins (2-sided die) can be used:

Die 1 1 4
Die 2 2 3

One of the two may be considered redundant. If mismatched, the set can be reduced to one coin and one "1-sided die".

Three players

An optimal and permutation-fair solution for 3 six-sided dice was found by Robert Ford in 2010.[1] There are several optimal alternatives using mismatched dice.

Numbers on each die
Die 1 1 5 10 11 13 17
Die 2 3 4 7 12 15 16
Die 3 2 6 8 9 14 18

Four players

An optimal and permutation-fair solution for 4 twelve-sided dice was found by Robert Ford in 2010. Alternative optimal configurations for mismatched dice were found by Eric Harshbarger.[1]

Numbers on each die
Die 1 1 8 11 14 19 22 27 30 35 38 41 48
Die 2 2 7 10 15 18 23 26 31 34 39 42 47
Die 3 3 6 12 13 17 24 25 32 36 37 43 46
Die 4 4 5 9 16 20 21 28 29 33 40 44 45

Five players

Several candidates exist for a set of 5 dice, but none is known to be optimal.

See also

References

  1. 1 2 3 4 5 Harshbarger, Eric (2015). "Go First Dice". Retrieved 9 Oct 2019.
  2. ↑ Bellos, Alex (18 Sep 2012). "Puzzler develops game-changing Go First dice". The Guardian. Retrieved 9 Oct 2019.
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