ANZIM

Anzim is an ant simulator.

General architecture

The world is a 2D grid of cells which may contain one or more of the following:

• nest: a nest will produce one ant per turn in which it can consume AF units of food; a nest dies if it drops below 0 units of food and there are no more ants;
• ant: an ant starts with AF health and will either move away from the nest (if not carrying food) or towards the nest (if carrying); at each step the ant consumes 1 unit of health and drops AT units of tracer; an ant dies if it drops below 0 units of health;
• food: food comes in packages of SF to BF food (by multiples of 2); it is picked up by ants and dropped in nests;
• tracer: tracer is dropped by ants and gets halved (round down) at every turn by evaporation;

Example parameters: AF = 256 (ant food/health) AT = 256 (ant tracer) SF = 1024 (small food package size) BF = 8192 (big food package size)

Limitations and behaviour

A cell can contain at most 1 nest, 2 ants and 2 packages of food of each size (see also the [Cannibal Rule][#cannibal-rule]).

An ant can carry at most one package of food, and will consume as much of it as necessary to bring its health back to AF if it drops below AF/2.

An ant carrying a package of food will pass it to an ant not carrying food and with not more than half (round up) of its health. Picking up, dropping (at the nest) or exchanging food costs one turn. One unit of food can restore one unit of health. Eating food costs one turn, but in a turn an ant can eat as much food as needed to restore health. An ant can pick food and eat it in the same turn.

Motion

Ants move randomly. Cells with higher tracer have higher probability. Ants will prefer moving in the same direction they came from. Specifically, each cell will have a weight d×(t+d), where t is the amount of tracer in the cell and d is the direction weight, ranging from 1 (cell the ant came from) to 16 (cell opposite the one the ant came from) in multiples of 2

Ants born at the nest will have d=1 for all cells. Ants that just picked up/dropped/exchanged food will prefer going back (d=32 for the cell they came from, d=1 for the opposite cell).

Conflict resolution

Motion

If more than two ants would move in the same cell, conflict are resolved according to the following criteria:

1. ants staying in the same cell have precedence;
2. ants being generated have precedence;
3. ants moving in from up, down, left, right have precedence over ants moving in from diagonal neighbouring cells;
4. ants with food have higher precedence;
5. ants with lower health have higher precedence;
6. ants for which the destination cell has higher weight have higher precedence.
7. ants with a higher ID (‘younger’) have higher precedence;

Some clarifications:

• a nest will not generate an ant if there are two ants staying on it;
• conflict resolution is an iterative process, since ants taking precendence over other ants may force the latter to stay, which may force other ants to stay, etc;
• on the next turn, ants that had to stay put due to conflict resolution will choose their new destination again, without particular preference for the location where they failed to move to.

Food package picking

If two ants are in the same cell, the lowest-health ant will pick the biggest available food package, and the other ant will pick the next available package (if any).

If both ants have the same health, and there is only one package of maximum available capacity, priority follows these criteria:

1. the ant that was already in the cell has precedence;
2. the ant that moved into the cell from up, down, left, right has precedence over the ant that moved in from a diagonal neighbouring cell;
3. the ant for which the destination cell has higher weight have higher precedence.
4. ants with a higher ID (‘younger’) have higher precedence;

Food generation

The world randomly generates food, using the following algorithm:

• each row and each column keeps track of the total number of food packages (regardless of size) not carried by ants;
• each row (resp. column) is weighted as 1 plus the total number of food packages in the row (resp. column) and its adjacent (next and previous) rows (resp. column);
• at every turn, a row, column pair (R, C) is randomly selected, following the respective weights;
• if all food package slots at (R, C) are full, or there is an ant in the cell, or the cell is a nest, no food is generated for this turn; otherwise, a pair of random numbers (RX, CX) in (-1, 0, 1) are picked;
• if RX = CX = 0 then a food package is generated at cell (R, C), otherwise no food is generated for this turn;
• if a food package is generated, its size is randomly picked based on the available food package slots.

(Rationale: generate food at a rate of about 1 in 9 turns, food is generated ‘close’ to existing food.)

(Question: should the generated package have a higher probability of being ‘close’ in size to the existing/neighbouring packages?)

Cannibal rule

Dead ants become packages with AF units of food. Dead ants do not count towards the row/column total, and they cannot be generated during normal food production. A cell can contain up to two dead ants.

(Rationale: no more than two ants can be dead in a cell, since a dying ant would pick one of the dead ants as food package and consume it to restore health.)

Main loop

1. Food generation
2. Ant generation/motion/action choice
3. Conflict resolution
4. World update