on-the-road-again

Demo

YouTube

Dependencies

Two dependencies are necessary to run this simulation:

• Python 3, accessible with the python3 shell command
• Erlang, accessible with the erl shell command

All other dependencies are handled by the Makefile.

Compiling and Running

The following Makefile rules are provided to automate running the simulation. They must be run from the build directory.

make

Installs all dependencies, compiles libraries and source code, then runs the simulation with a medium-size road graph.

make dependencies

Installs all necessary dependencies for the project, including the python libraries grandalf, tomli, pygame, and erlastic. Furthermore, it builds the toml erlang library using that library's Makefile.

make traffic.beam

Builds the non-library erlang code that runs the actual simulation.

make run

Runs the simulation with a moderately sized road graph

make <*.toml>

Runs the simulation with the roads file provided. The .toml file must be in the roads directory.

make clean

Cleans up all build files. Also cleans up compiled libraries.

Config format

Clients can specify their own custom road networks using a TOML config file, and can pass that file to the make command to simulate the road network (see above).

• Intersections are stored in the intersections field, which is a flat list of strings.
• Roads are stored in roads, which is a list of pairs of intersection names. The first name in the pair specifies the source intersection, and the second is the destination.
• Individual cars are defined underneath a [[cars]] header. A car has a floating-point field called speed, and two string fields called start and end.

See the roads/ directory for example configuration files.

Overview of source code

All code can be found in src/, with the exception of build/Makefile

• car.erl
  • an actor representation of a car; moves along roads, and contacts intersections along its route and waits to be signaled
  • traffic.erl uses this module to launch car processes
• car.py
  • a very simple object-oriented representation of a car
  • used by display.py to package together data about cars
• clock.erl
  • sends periodic messages to the python visualization
  • used by display.py to synchronize with backend during idle time
• display.py
  • initializes visualization
  • scales graph embedding to fit nicely on display
  • Handshakes with erlang to confirm connection
  • Listens to updates from erlang and modifies the displayed image to match
• embed_graph.py
  • Performs graph embedding of the directed graph
  • exports a dictionary mapping intersections to points
• intersection.erl
  • actor representation of an intersection, which rotates through queues of waiting cars and signals them
  • traffic.erl uses this module to launch intersection processes
• build/Makefile
  • rules to verify and install dependencies
  • rules to run the simulation
• ports.erl
  • contains tools for communicating with the python visualization
  • used by car, intersection, and traffic modules to send updates to python sim_state.py
    • a bloated monstrosity for passing the initial configuration from the toml file to the graph embedding algorithm.
    • a class is not necessary here, but Liam wanted practice
• traffic.erl
  • loads a road network from a TOML file and launches visualization, roads, and intersections gets run by the client to start everything off
• visualization.py
  • the visualization “driver”
  • contains the target script that is invoked when the Erlang port is opened