Hopper

This Environment is part of MaMuJoCo environments. Please read that page first for general information. The task is Gymansium’s MuJoCo/Hopper.

Action Space

The shape of the action space depends on the partitioning. The partitioning has the following form:

if partitioning is None:

Instantiate	env = mamujoco_v1.parallel_env("Hopper", None)
Agents	agents= ['agent_0']
Number of Agents	1
Action Spaces	{'agent_0' : Box(-1, 1, (3,), float32)}
Part partition	[(thigh_joint, leg_joint, foot_joint,)]

If partitioning, is None, then the environment contains a single agent with the same action space as Gymansium’s MuJoCo/Half_Cheetah.

Num	Action	Control Min	Control Max	Name (in corresponding XML file)	Joint	Unit
0	Torque applied on the thigh rotor	-1	1	thigh_joint	hinge	torque (N m)
1	Torque applied on the leg rotor	-1	1	leg_joint	hinge	torque (N m)
2	Torque applied on the foot rotor	-1	1	foot_joint	hinge	torque (N m)

if partitioning == “3x1”: # each joint

Instantiate	env = mamujoco_v1.parallel_env("Hopper", "3x1")
Agents	agents= ['agent_0', 'agent_1', 'agent_2']
Number of Agents	3
Action Spaces	{Box(-1, 1, (1,), float32)}
Part partition	[(thigh_joint,), (leg_joint,), (foot_joint,)]

The environment is partitioned in 3 parts, each part corresponding to a single joint.

Agent 0 action space

Num	Action	Control Min	Control Max	Name (in corresponding XML file)	Joint	Unit
0	Torque applied on the thigh rotor	-1	1	thigh_joint	hinge	torque (N m)

Agent 1 action space

Num	Action	Control Min	Control Max	Name (in corresponding XML file)	Joint	Unit
0	Torque applied on the leg rotor	-1	1	leg_joint	hinge	torque (N m)

Agent 2 action space

Num	Action	Control Min	Control Max	Name (in corresponding XML file)	Joint	Unit
0	Torque applied on the foot rotor	-1	1	foot_joint	hinge	torque (N m)

Observation Space

Observation Categories
Default local_categories	[["qpos", "qvel"], ["qpos"]]
Default global_categories	("qpos", "qvel")
Supported observation categories	"qpos", "qvel"

Besides the local observation of each agent (which depend on their parts of the agent, the observation categories and the observation depth), each agent also observes the position and velocity items of the hopper’s top. See more at the Gymnasium’s Hopper.

Rewards

All agents receive the same Gymnasium’s Hopper reward.

Starting state

The starting state of the environment is the same as Gymnasium’s Hopper.

Episode End

All agent terminate and truncate at same time given the same conditions as Gymnasium’s Hopper.

Version History

• v1:

  • Now based on Gymnasium/MuJoCo-v5 instead of Gymnasium/MuJoCo-v4 (https://github.com/Farama-Foundation/Gymnasium/pull/572).

• v0: Initial version release, uses Gymnasium.MuJoCo-v4, and is a fork of the original MaMuJoCo schroederdewitt/multiagent_mujoco. Changes from the original MaMuJoCo (schroederdewitt/multiagent_mujoco):

  • Fixed Global observations (The Hopper’s top: rootx, rooty, rootz) not being observed.