Team Battle

The Team Battle scenario involves multiple teams of agents fighting against each other. The goal of each team is to be the last team alive, at which point the simulation will end. Each agent can move around the grid and attack agents from other teams. Each agent can observe the grid around its position. We will reward each agent for successful kills and penalize them for bad moves. This tutorial can be found in full in our repo.

Video showing teams fighting.

Agents on four teams battling each other.

First, we import the components that we need. Each component is already in Abmarl, so we don’t need to create anything new.

from matplotlib import pyplot as plt
import numpy as np

from abmarl.sim.gridworld.base import GridWorldSimulation
from abmarl.sim.gridworld.agent import GridObservingAgent, MovingAgent, AttackingAgent, HealthAgent
from abmarl.sim.gridworld.state import HealthState, PositionState
from abmarl.sim.gridworld.actor import MoveActor, BinaryAttackActor
from abmarl.sim.gridworld.observer import SingleGridObserver
from abmarl.sim.gridworld.done import OneTeamRemainingDone

Then, we define our agent types. This simulation will only have a single type: the BattleAgent. Most of the agents’ attributes will be the same, and we can preconfigure the class definition to save us time when we create the agents later on.

class BattleAgent(GridObservingAgent, MovingAgent, AttackingAgent, HealthAgent):
    def __init__(self, **kwargs):
        super().__init__(
            move_range=1,
            attack_range=1,
            attack_strength=1,
            attack_accuracy=1,
            view_range=3,
            **kwargs
        )

Having defined the BattleAgent, we then put all the components together into a single simulation.

class TeamBattleSim(GridWorldSimulation):
    def __init__(self, **kwargs):
        self.agents = kwargs['agents']

        # State Components
        self.position_state = PositionState(**kwargs)
        self.health_state = HealthState(**kwargs)

        # Action Components
        self.move_actor = MoveActor(**kwargs)
        self.attack_actor = BinaryAttackActor(**kwargs)

        # Observation Components
        self.grid_observer = SingleGridObserver(**kwargs)

        # Done Compoennts
        self.done = OneTeamRemainingDone(**kwargs)

        self.finalize()

Next we define the start state of each simulation. We lean on the State Components to perform the reset. Note that we must track the rewards explicitly.

class TeamBattleSim(GridWorldSimulation):
    ...

    def reset(self, **kwargs):
        self.position_state.reset(**kwargs)
        self.health_state.reset(**kwargs)

        # Track the rewards
        self.rewards = {agent.id: 0 for agent in self.agents.values()}

Then we define how the simulation will step forward, leaning on the Actors to process their part of the action. The Actors’ result determine the agents’ rewards.

class TeamBattleSim(GridWorldSimulation):
    ...

    def step(self, action_dict, **kwargs):
        # Process attacks:
        for agent_id, action in action_dict.items():
            agent = self.agents[agent_id]
            attacked_agent = self.attack_actor.process_action(agent, action, **kwargs)
            if attacked_agent is not None:
                self.rewards[attacked_agent.id] -= 1
                self.rewards[agent.id] += 1
            else:
                self.rewards[agent.id] -= 0.1

        # Process moves
        for agent_id, action in action_dict.items():
            agent = self.agents[agent_id]
            if agent.active:
                move_result = self.move_actor.process_action(agent, action, **kwargs)
                if not move_result:
                    self.rewards[agent.id] -= 0.1

        # Entropy penalty
        for agent_id in action_dict:
            self.rewards[agent_id] -= 0.01

Finally, we define each of the getters using the Observers and Done components.

class TeamBattleSim(GridWorldSimulation):
    ...

    def get_obs(self, agent_id, **kwargs):
        agent = self.agents[agent_id]
        return {
            **self.grid_observer.get_obs(agent, **kwargs)
        }

    def get_reward(self, agent_id, **kwargs):
        reward = self.rewards[agent_id]
        self.rewards[agent_id] = 0
        return reward

    def get_done(self, agent_id, **kwargs):
        return self.done.get_done(self.agents[agent_id])

    def get_all_done(self, **kwargs):
        return self.done.get_all_done(**kwargs)

    def get_info(self, agent_id, **kwargs):
        return {}

Now that we’ve defined our agents and simulation, let’s create them and run it. First, we’ll create the agents. There will be 4 teams, so we want to color the agent by team and start them at different corners of the grid. Besides that, all agent attributes will be the same, and here we benefit from preconfiguring the attributes in the class definition above.

colors = ['red', 'blue', 'green', 'gray'] # Team colors
positions = [np.array([1,1]), np.array([1,6]), np.array([6,1]), np.array([6,6])] # Grid corners
agents = {
    f'agent{i}': BattleAgent(
        id=f'agent{i}',
        encoding=i%4+1,
        render_color=colors[i%4],
        initial_position=positions[i%4]
    ) for i in range(24)
}

Having created the agents, we can now build the simulation. We will allow agents from the same team to occupy the same cell and allow agents to attack other agents if they are on different teams.

overlap_map = {
    1: [1],
    2: [2],
    3: [3],
    4: [4]
}
attack_map = {
    1: [2, 3, 4],
    2: [1, 3, 4],
    3: [1, 2, 4],
    4: [1, 2, 3]
}
sim = TeamBattleSim.build_sim(
    8, 8,
    agents=agents,
    overlapping=overlap_map,
    attack_mapping=attack_map
)

Finally, we can run the simulation with random actions and visualize it. The visualization produces an animation like the one at the top of this page.

sim.reset()
fig = plt.figure()
sim.render(fig=fig)

done_agents = set()
for i in range(50): # Run for at most 50 steps
    action = {
        agent.id: agent.action_space.sample() for agent in agents.values() if agent.id not in done_agents
    }
    sim.step(action)
    sim.render(fig=fig)

    if sim.get_all_done():
        break
    for agent in agents:
        if sim.get_done(agent):
            done_agents.add(agent)

Extra Challenges

Having successfully created and run a TeamBattle simulation, we can further explore the GridWorldSimulation framework. Some ideas are:

  • Experiment with the number of agents and the impact that has on both the SingleGridObserver and the MultiGridObserver.

  • Experiment with the number of agents per team as well as the capabilities of those agents. You might find that a super capable agent is still effective against a team of multiple agents.

  • Create a Hunter-Forager simulation, where one team of agents act as immobile resources that can be foraged by another team, which can be hunted by a third team. Try using the same components here, although you may need to use a custom done condition.

  • Connect this simulation with the Reinforcement Learning capabilities of Abmarl via a Simulation Manager. What kind of behaviors do the agents learn?

  • And much, much more!