IPC track for HTN Planning

The 2020 IPC for Hierarchical Planning

ICAPS 2020 will host the 2020 IPC for Hierarchical Planning - as proposed in the following paper. It will be the first IPC solely dedicated to Hierarchical Planning and HTN Planning in particular.

The 2020 IPC for Hierarchical Planning will feature three tracks:

  1. total-order, non-recursive
  2. total-order, recursive
  3. partial-order, recursive

All tracks share common restrictions on the input:

  • All actions have only STRIPS-style preconditions and effects,
  • all actions have unit-cost, and
  • methods may contain preconditions (but no other state constraints).

Input Language

The competition will use domains and problems formulated in HDDL. Its syntax and semantics are explained in a recent workshop paper. For convenience, we will provide an automated translation of HDDL into (J)SHOP2 syntax. Note that there are domains which can be expressed in HDDL, but for which there is no equivalent SHOP2 model. The issue lies in the restrictions SHOP2 puts on the allowed ordering. If you want to participate and need any other input format, please contact us as soon as possible s.t. we can assist you as best as possible.

A set of sample problem is available here. It includes two domains (transport and rover) in four different configurations:

  • totally-ordered as HDDL
  • partially-ordered as HDDL
  • totally-ordered as SHOP2
  • partially-ordered as SHOP2

The rover domain is non-recursive, while transport is recursive. If you have any issues with or questions about these sample, please contact us!

The SHOP2-variants of the instances were generated automatically. The code for this translation is part of the pandaPI planning system, more specifically its parser. Its code is available on github.

Evaluation and Technical Specification

To evaluate planners, we will use the agile metric used in the last IPC, i.e. a planner is regarded better wrt that metric if it finds any solution to the problem faster.
The score of a planner on a solved task is 1 if the task was solved within 1 second and 0 if the task was not solved within the resource limits. If the task was solved in t seconds (1 \leq t \leq T) with a timelimit of T seconds then its score is min{1, 1 - log(t)/log(T)}. The score of a planner is the sum of its scores for all tasks.

All tracks will share the following techical specifications:

  • 1 CPU core
  • X GB memory limit (not yet known definitively)
  • T min time limit (not yet known definitively)
  • If an invalid plan is returned, all tasks in the domain are counted as unsolved.
  • If that happens in more than one domain, the entry is disqualified.

For the specification of the tracks we mean with

  • total-order: A domain is *totally ordered* iff the subtasks in all methods and in the initial task network form a sequence, i.e. the declared ordering arranges the tasks in a sequence.
  • partial-order: A domain is *totally ordered* iff the subtasks in all methods and in the initial task network may have any order that can be specified in HDDL.
  • non-recursive: A domain is *non-recursive* if there is a total order on its lifted tasks (primitive and abstract) such that for every method that decomposes an abstract task A, the tasks in the methods' task network occur after A in the total order.
  • recursive: A domain that is not non-recursive
  • STRIPS actions: We consider an action to be STRIPS, if both its preconditions and effects are lists of literals. I.e. preconditions and effects do not contain quantors, disjunctions, or conditional effects. However negative preconditions are allowed.
  • Method precondition: A list of literals that may be associated with a method. A method may only be applied if its method precondition holds. For totally-ordered HTN planning problems, the precondition has to hold in the state in which the first action (that originates via further decompositions from the method's subtasks) is executed. For partially-ordered HTN planning problems, the precondition has to hold in some state before the first action (that originates via further decompositions from the methods' subtasks) is executed, but after the state resulting from the last necessarily preceding tasks for the tasks contained in the method.

Timetable

Call for interest September 30th
Announcement of Tracks October 18th
Demo domains and problems are available (including a (J)SHOP2 translator) October 22nd
Output-format specification November 29nd
Initial submission of planners January 31st
Deadline for domain submissions February 29th
Final submission of planners approx end of April
Presentation of Results June 14th-19th

Organisers

Note that we also have a mailing list for everyone who is interested in hierarchical planning (including non-standard HTN planning), so this list in independent of this IPC endeavor. If you want to join this moderated, SPAM-free list, please write an email to Pascal Bercher.