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#!/usr/bin/env python3
import numpy as np
from gym import spaces
from gym.utils import seeding
from learn2learn.gym.envs.meta_env import MetaEnv
class Particles2DEnv(MetaEnv):
"""
[[Source]](https://github.com/learnables/learn2learn/blob/master/learn2learn/gym/envs/particles/particles_2d.py)
**Description**
Each task is defined by the location of the goal. A point mass
receives a directional force and moves accordingly
(clipped in [-0.1,0.1]). The reward is equal to the negative
distance from the goal.
**Credit**
Adapted from Jonas Rothfuss' implementation.
"""
def __init__(self, task=None):
self.seed()
super(Particles2DEnv, self).__init__(task)
self.observation_space = spaces.Box(low=-np.inf, high=np.inf,
shape=(2,), dtype=np.float32)
self.action_space = spaces.Box(low=-0.1, high=0.1,
shape=(2,), dtype=np.float32)
self.reset()
# -------- MetaEnv Methods --------
def sample_tasks(self, num_tasks):
"""
Tasks correspond to a goal point chosen uniformly at random.
"""
goals = self.np_random.uniform(-0.5, 0.5, size=(num_tasks, 2))
tasks = [{'goal': goal} for goal in goals]
return tasks
def set_task(self, task):
self._task = task
self._goal = task['goal']
# -------- Gym Methods --------
def seed(self, seed=None):
self.np_random, seed = seeding.np_random(seed)
return [seed]
def reset(self, env=True):
"""
Sets point mass position back to (0,0)
"""
self._state = np.zeros(2, dtype=np.float32)
return self._state
def step(self, action):
"""
**Description**
Given an action, clips the action to be in the
appropriate range and moves the point mass position
according to the action.
**Arguments**
action (2-element array) - Array specifying the magnitude
and direction of the forces to be applied in the x and y
planes.
**Returns**
*state, reward, done, task*
* state (arr) - is a 2-element array encoding the x,y position of
the point mass
* reward (float) - signal equal to the negative squared distance
from the goal
* done (bool) - boolean indicating whether or not the point mass
is epsilon or less distance from the goal
* task (dict) - dictionary of task specific parameters and their current
values
"""
action = np.clip(action, -0.1, 0.1)
assert self.action_space.contains(action)
self._state = self._state + action
x = self._state[0] - self._goal[0]
y = self._state[1] - self._goal[1]
reward = -np.sqrt(x ** 2 + y ** 2)
done = ((np.abs(x) < 0.01) and (np.abs(y) < 0.01))
return self._state, reward, done, self._task
def render(self, mode=None):
raise NotImplementedError
You can’t perform that action at this time.