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Utilities for the CG:SHOP 2021 Optimization Competition on Coordinated Motion Planning.

Project description

Official Python Utilities for the CG:SHOP 2021 Optimization Competition.

We provide basic code to ease your participation in this year's challenge. Due to it popularity and simplicity, the choice has fallen on Python.

This python module allows you to easily read the instance and potentially convert them into an easier format. The JSON format is simple but it is very common and allows to easily add metadata. Further, this module allows you to verify your instances. It uses the same core as the server so if this code accepts your solution, so will our server.

The code is not perfect but we will work to improve this code during the competition. Feedback is welcome.

This time, the code is pure Python and should run on all machines. The source code will be soon published. We are currently deciding for the right platform (probably GitHub).


  • Reading and writing instance files.
  • Reading and writing solution files.
  • Verifying solutions for feasibility.

The exact same implementation will be used on the submission server. Thus, if this library will accept your solution, so will the submission server.


The installation is trivial using pip.

pip install cgshop2021-pyutils

Note that you have to use _ instead of - when importing the module.

Maybe you need to add to --user flag to save the package into your home directory instead of the system's directory.

You will also be able to simply copy the source code into your code without any installation. However, please keep this library updated as there will probably be some forgotten corner cases. (Actually, at the time I am writing this, the code has not been properly tested as we had to prioritize instance generation and the server. Give us a few days.)

pip install cgshop2021-pyutils --upgrade

Reading the instances from the Zip

Best use the instance database. You simply download the .zip and then you can access all instances via

from cgshop2021_pyutils import InstanceDatabase
idb = InstanceDatabase("path/to/")
for i in idb:
    print("Instance:", i)

Working with an instance

from cgshop2021_pyutils import Instance

i: Instance #just to enable typing

for r in range(i.number_of_robots):
    print("Robot", i, "starts at", i.start_of(r)," and has to go to ", i.target_of(r))

for o in i.obstacles:
    print(o, "is blocked")

Create a solution

from cgshop2021_pyutils import Solution, SolutionStep, SolutionZipWriter, Direction
from cgshop2021_pyutils import Instance

instance: Instance
solution = Solution(instance) 

# First time step in the solution
step_1 = SolutionStep()
step_1[2]=Direction.NORTH # Robot 2 moves north
step_1[1]=Direction.WEST # Robot 1 moves west

# Second time step in the solution
step_2 = SolutionStep()
step_2[0]=Direction.SOUTH # Robot 0 moves north
step_2[2]=Direction.WEST # Robot 2 moves west

print("Makespan:", solution.makespan)

print("SUM:", solution.total_moves)

Write solutions

You can easily write solutions to an uploadable zip.

from cgshop2021_pyutils import SolutionZipWriter, Solution
s1: Solution
s2: Solution
s3: Solution

with SolutionZipWriter("") as szw:
    szw.add_solutions([s1, s2])

Validate your solution

Solutions can be validate via validate. This function does not return anything but will throw an exception if something is wrong. The exception will contain an explanation (by type and message).

from cgshop2021_pyutils import InstanceDatabase, ZipSolutionIterator, validate, ZipReaderError, InvalidSolutionError, SolutionEncodingError
idb = InstanceDatabase("path/to/")
    for solution in ZipSolutionIterator(idb)("/path/to/"):
except ZipReaderError as zre:
    print("Bad Zip:", zre)
except InvalidSolutionError as ise:
    print("Bad Solution:", ise)
except SolutionEncodingError as see:
    print("Bad Solution File:", see)

Version History

  • 0.0.1-0.0.5: Beta Versions
  • 0.1.0: First officially used version.
  • 0.1.1: Increased allowed zip size.

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