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vetrov_andrew 14h Hi everyone!

I would like to report a bug of Flatland 2.0, connected with stochastic events.

As you can see, a stochastic event occurs with my agent on the first step. Then my agent waits for several steps, sending to the system “4” (or nothing).

However, when this stochastic event ends, something throws the agent out of railway system (or out of a map in my example). You can see that position of the agent is (-1, 2).

Note that this problem occurs in many different cases when an agent waits during stochastic event is ending.

Simulate the bug with following code (just copy to jupyter):

import time
from flatland.envs.observations import TreeObsForRailEnv
from flatland.envs.predictions import ShortestPathPredictorForRailEnv
from flatland.envs.rail_env import RailEnv
from flatland.envs.rail_generators import sparse_rail_generator
from flatland.envs.schedule_generators import sparse_schedule_generator
from flatland.utils.rendertools import RenderTool


stochastic_data = {'prop_malfunction': 1.,  # Percentage of defective agents
                   'malfunction_rate': 70,  # Rate of malfunction occurence
                   'min_duration': 2,  # Minimal duration of malfunction
                   'max_duration': 5  # Max duration of malfunction
                   }

speed_ration_map = {1.: 1.,  # Fast passenger train
                    1. / 2.: 0.,  # Fast freight train
                    1. / 3.: 0.,  # Slow commuter train
                    1. / 4.: 0.}  # Slow freight train


env = RailEnv(width=25,
              height=30,
              rail_generator=sparse_rail_generator(num_cities=5,  # Number of cities in map (where train stations are)
                                                   num_intersections=4,  # Number of intersections (no start / target)
                                                   num_trainstations=25,  # Number of possible start/targets on map
                                                   min_node_dist=6,  # Minimal distance of nodes
                                                   node_radius=3,  # Proximity of stations to city center
                                                   num_neighb=3,  # Number of connections to other cities/intersections
                                                   seed=215545,  # Random seed
                                                   grid_mode=True,
                                                   enhance_intersection=False
                                                   ),
              schedule_generator=sparse_schedule_generator(speed_ration_map),
              number_of_agents=1,
              stochastic_data=stochastic_data,  # Malfunction data generator
              )



env_renderer = RenderTool(env)
env_renderer.render_env(show=True, frames=False, show_observations=False)
_action = dict()

for step in range(4):
    #_action[0] = 4
    obs, all_rewards, done, info = env.step(_action)
    print(info["malfunction"][0])
    print(env.agents[0].position)
    env_renderer.render_env(show=True, frames=False, show_observations=False)
    time.sleep(0.1)
print("Here position of the agent is invalid")

Thank you for fixing this bug. Hope, it won`t be difficult.