Changes since Flatland 2.0.0

Changes in Environment

  • moving of member variable distance_map_computed to new class DistanceMap

Changes in rail generator and RailEnv

  • renaming of distance_maps into distance_map

Changes since Flatland 1.0.0

Changes in stock predictors

The stock ShortestPathPredictorForRailEnv now respects the different agent speeds and updates their prediction accordingly.

Changes in stock observation biulders

  • TreeObsForRailEnv now has 11 features!
    • 10th feature now indicates if a malfunctioning agent has been detected and how long the malfunction will still be present
    • 11th feautre now indicates the minimal observed fractional speed of agents traveling in the same direction
  • GlobalObsForRailEnv now has new features!
    • Targets and other agent targets still represented in same way
    • obs_agents_state now contains 4 channels
      • 0th channel -> agent direction at agent position
      • 1st channel -> other agents direction at their positions
      • 2nd channel -> all agent malfunction duration at their positions
      • 3rd channel -> all agent fractional speeds at their positions
  • LocalObsForRailEnv was not update to Flatland 2.0 because it was never used by participants of the challenge.

Changes in level generation

  • Separation of schedule_generator from rail_generator:
    • Renaming of flatland/envs/ to flatland/envs/
    • rail_generator now only returns the grid and optionally hints (a python dictionary); the hints are currently use for distance_map and communication of start and goal position in complex rail generator.
    • schedule_generator takes a GridTransitionMap and the number of agents and optionally the agents_hints field of the hints dictionary.
    • Inrodcution of types hints:
RailGeneratorProduct = Tuple[GridTransitionMap, Optional[Any]]
RailGenerator = Callable[[int, int, int, int], RailGeneratorProduct]
AgentPosition = Tuple[int, int]
ScheduleGeneratorProduct = Tuple[List[AgentPosition], List[AgentPosition], List[AgentPosition], List[float]]
ScheduleGenerator = Callable[[GridTransitionMap, int, Optional[Any]], ScheduleGeneratorProduct]

Multi Speed

  • Different agent speeds are introduced. Agents now travel at a max speed which is a fraction. Meaning that they only advance parts within a cell and need several steps to move to the next cell.
    • Fastest speed is 1. At this speed an agent can move to a new cell at each time step t.
    • Slower speeds are smaller than one. At each time step an agent moves the fraction of its speed forward within a cell. It only changes cell when it’s fractional position is greater or equal to 1.
    • Multi-speed introduces the challenge of ordering the trains correctly when traveling in the same direction.
  • Agents always travel at their full speed when moving.

To set up multiple speeds you have to modify the agent.speed_data within your schedule_generator. See this file for a good example.

ATTENTION multi speed means that the agents actions are not registered on every time step. Only at new cell entry can new actions be chosen! Beware to respect this with your controller as actions are only important at the specific time steps! This is shown as an example in the navigation training

Stochastic events

Just like in real-worl transportation systems we introduced stochastic events to disturb normal traffic flow. Currently we implemented a malfunction process that stops agents at random time intervalls for a random time of duration. Currently the Flatland environment can be initiated with the following poisson process parameters:

# Use a the malfunction generator to break agents from time to time
stochastic_data = {'prop_malfunction': 0.1,  # Percentage of defective agents
                   'malfunction_rate': 30,  # Rate of malfunction occurence
                   'min_duration': 3,  # Minimal duration of malfunction
                   'max_duration': 20  # Max duration of malfunction

The duration of a malfunction is uniformly drawn from the intervall [min_duration,max_duration0] and the occurance of malfunctions follows a point poisson process with mean rate malfunctin_rate.

!!!!IMPORTANT!!!! Once a malfunction duration has finished, the agent will automatically resume movement. This is important because otherwise it can get stuck in fractional positions and your code might forget to restart the agent at the first possible time. Therefore this has been automated. You can however stop the agent again at the next cell. This might in rare occasions lead to unexpected behavior, we are looking into this and will push a fix soon.

Baselines repository

The baselines repository is not yet fully updated to handle multi-speed and stochastic events. Training needs to be modified to omitt all states inbetween the states where an agent can chose an action. Simple navigation training is already up to date. See here for more details.

Changes since Flatland 0.2

Please list all major changes since the last version:

  • Refactoring of rendering code: CamelCase functions changed to snake_case
  • Tree Observation Added a new Featuer: unusable_switch which indicates switches that are not branchingpoints for the observing agent
  • Updated the shortest path predictor
  • Updated conflict detection with predictor
  • Episodes length can be set as maximum number of steps allowed.