Introduction

This is a second pass at the chess problem we solved in Python, using this time domain independent planning in PDDL.

Incidentally, this method runs a lot faster than the Python version (on my computer, tenths of seconds vs. 15-20 seconds).

Notice also that unlike ML-based approaches, actions are scrutable - meaning that human beings can understand why the planner chooses to do what it does.

Files

The main three files of interest are:

• domain.pddl that models a very much simplified game of chess, where we are only modeling pieces colors and movements.
• problem.pddl that models the chess problem, and in particular
  • models the initial state of the chess board, square by square
  • models the moves that are allowed as knights
  • expresses the goal of switching the black and white knights
• chess_ap.pddl that models the visualization of the problem being solved.

This is a very quick attempt at modeling the domain and problem, both can surely be made a lot more elegant.

Trying it out

• Go to the very good PDDL Editor

• You will find there the three files mentioned above. If they are missing, load them manually.

• Click on Solve, then Plan. You should see a plan come up on the left pane, Plan (I), with a plan that solves the problem.

• Better yet, visualize the moves. The Planimation plugin should be loaded. If it is not, load it via the Plugins menu (yep, plugin loading fails sometimes). You should get this menu: Click on Planimation, then Planimate leaving the default options You should get this window: Click on "play" and enjoy

• Even better, watch the Heuristic function at work. Click on HeurViz, then Go. You should have a new file, Statespace on the left, go there. Click on Compute All Heuristics on the right. Notice how you can double-click on a node to search further and ask again to Compute All Heuristics, to see how the planner is progressing in the search space. A tooltip will give you the heuristic on a node:

  Going further

  • You can start by editing the PDDL files using the PDDL Editor.

  • Next step, if you want to use new graphics, drop PNG files in the img folder then run Make. To get Make, either install it or use the Devcontainer configuration that is provided.