Unsolvability International Planning Competition

./plan domain.pddl problem.pddl

The aim of the unsolvability IPC is to test the ability of classical automated planners to detect when a planning task has no solution. The benchmarks used in the track will contain a mix of solvable and unsolvable instances, and points will only be awarded for correctly identifying the unsolvable instances.

Mailing List: https://groups.google.com/forum/#!forum/ipc2016-unsolvability


Event Date
Announcement of the trackJun, 2015
Call for domains / expression of interestAug, 2015
Demo problems providedNov, 2015
(optional) Initial feedback on buggy outputFeb, 2016
Domain submission deadlineFeb, 2016
Final planner submission deadlineMar, 2016
Paper submission deadline May, 2016
Contest runApr - May, 2016
Results announced in LondonJun, 2016


Some details on how the planners must behave:

  • Planners will be limited to 8Gb of memory and 30min solve time.
  • The planner should only provide one of three messages to standard output: solvable, unsolvable, or unknown.
  • You can use this plan script that returns "unknown" when your planner fails giving an answer.


Example unsolvable instances can be found [here]. The first two problems are small instances detected by most planners (one without a delete relaxed solution), and the latter two are larger instances that exhibit the same behaviour.

While not every benchmark domain will be of this form, an ideal domain will have the following properties:

  1. A mix of solvable and unsolvable problems
  2. No obvious (i.e., syntactic) distinction between the solvable and unsolvable instances
  3. At least some of the solvable instances are difficult to solve using state-of-the-art planners

The properties are meant to dissuade inappropriate entries that return 'Unsolvable' when a problem is too difficult to find a plan for -- false positives will be penalized heavily.


The primary focus will be on the coverage of problems correctly identified as having no solution. Ties will be broken based on the standard IPC time score for the unsolvable instances. There will be no points awarded for the solvable instances in the domain sets -- they are there primarily to deter from simply returning 'Unsolvable' for every problem.

Similar to the deterministic optimal IPC track, a solver will be disqualified for a domain if it returns a false positive (saying 'Unsolvable' when the problem is in fact solvable).


Competition Presentation Slides announced in London

Git Repository containing Solvers, Papers, Domains, Eval Setup, and relevant information

DataJoy project containing all the statistics / analysis (tip: to see results, run the script in datajoy)

Planners Description (PDF)