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Connector Environment#

The Connector environment contains multiple agents spawned in a grid world with each agent representing a start and end position that need to be connected. The main goal of the environment is to connect each start and end position in as few steps as possible. However, when an agent moves it leaves behind a path, which is impassable by all agents. Thus, agents need to cooperate in order to allow each other to connect to their own targets without overlapping.

An episode ends when all agents have connected to their targets or no agents can make any further moves due to being blocked.

Observation#

At each step observation contains 3 items: a grid, an action mask for each agent and the episode step count.

  • grid: jax array (int32) of shape (grid_size, grid_size), a 2D matrix that represents pairs of points that need to be connected. Each agent has three types of points: position, target and path which are represented by different numbers on the grid. The position of an agent has to connect to its target, leaving a path behind it as it moves across the grid forming its route. Each agent connects to only 1 target.

  • action_mask: jax array (bool) of shape (num_agents, 5), indicates which actions each agent can take.

  • step_count: jax array (int32) of shape (), represents how many steps have been taken in the environment since the last reset.

Encoding#

Each agent has 3 components represented in the observation space: position, target, and path. Each agent in the environment will have an integer representing their components.

  • Positions are encoded starting from 2 in multiples of 3: 2, 5, 8, …

  • Targets are encoded starting from 3 in multiples of 3: 3, 6, 9, …

  • Paths appear in the location of the head once it moves, starting from 1 in multiples of 3: 1, 4, 7, …

Every group of 3 corresponds to 1 agent: (1,2,3), (4,5,6), …

Example: 

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2
3
Agent1[path=1, position=2, target=3]
Agent2[path=4, position=5, target=6]
Agent3[path=7, position=8, target=9]

For example, on a 6x6 grid, a possible observation is shown below.

1
2
3
4
5
6
[[ 2  0  3  0  0  0]
 [ 1  0  4  4  4  0]
 [ 1  0  5  9  0  0]
 [ 1  0  0  0  0  0]
 [ 0  0  0  8  0  0]
 [ 0  0  6  7  7  7]]

Action#

The action space is a MultiDiscreteArray of shape (num_agents,) of integer values in the range of [0, 4]. Each value corresponds to an agent moving in 1 of 4 cardinal directions or taking the no-op action. That is, [0, 1, 2, 3, 4] -> [No Op, Up, Right, Down, Left].

Reward#

The reward is dense: +1.0 per agent that connects at that step and -0.03 per agent that has not connected yet.

Rewards are provided in the shape (num_agents,) so that each agent can have a reward.

Registered Versions 📖#

  • Connector-v2, grid size of 10 and 10 agents.
Last update: 2024-03-29
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