International Planning Competition 2023 HTN Tracks

IPC 2023 HTN Tracks

International Planning Competition 2023 HTN Tracks

This is the website for the hierarchical (HTN) tracks of the IPC 2023. It is the 2nd IPC containing hierarchical tracks, after its first occurance in 2020.


Please forward the following calls to all interested parties.


Event Date
Call for domains October 12, 2022
Call for participation October, 2022
Domain expression of interest deadline December 31, 2022
Domain submission deadline February 28, 2023
Demo problems provided February 10, 2023
Initial planner submission February 28, 2023
Feature stop (final planner submission) May, 2023
Planner Abstract submission deadline May, 2023
Contest run June, 2023
Results announced July 12, 2023
Result analysis deadline August, 2023


There will be (up to, provided sufficient interesst) six tracks in IPC’s HTN track. These are:

The semantics of these tracks is explained in the following.



Agile Track

Satisficing Track

Optimal Track

HDDL Fragment

We will use the same input language as the previous HTN IPC 2020

Technical Issues.

Competitors are required to submit their code via a github repository that was set up by the track’s organisers. At the time of submission, these repositories will be private and will be made public after the competition results have been announced.

Until the feature stop (see Schedule) competitors can make any change to their planners. After the feature stop, competitors are only allowed to send pull requests with bug fixes. We will review every pull request with its accompanying description of the bug fix to make sure that no significant changes or parameter tuning are possible.

As in 2020, we will provide a continous integration system. We will run planners on sample problems and publish the resulting outputs. To faciliate the detection of anomalies, each competitor is required to also submit a script that validates the planners output and that is responsible to highlight (potential) errors that need to be investigated.

As in the HTN IPC of 2020, we will use the container software Apptainer (formerly known as Singularity) to promote reproducibility and simplify program compilation. You can find the documentation on how the Apptainer files are written here.

We will automatically extract the configurations you want to submit from your repository. We create one configuration per Apptainer file in the root directory of your repository. Apptainer files are files whose file ending is .def.


In order to participate in the HTN IPC, you need to register until February 28, 2023. To do so, please send an email to Gregor Behnke containing the following information

As the other IPC tracks, the HTN track allows for multiple submissions to use the same planner codebase. These submissions can, e.g., differ in the configuration of the planner such as the used heuristic(s) or search techniques. Each of these configurations will (most likely) be a separate apptainer definition file (formerly Singularity file).

The number of submissions per participant (natural person who participates) is limited to three per track. That means that any person may only be named as a “participant” for at most three submission per track. This limit applies to the number of configurations and not codebases. I.e. the limit is already reached if a participant submits one codebase that is used for three configurations in one track.

After some discussion we have decided to update and clarify the submission rules as follows (on 24-02-2023):

Authors are allowed to submit an arbitrary number – within reason – of different planning systems per track. Two planning systems are considered different if the relevant codebase, i.e., the parts of the code that are actually being executed, differs substantially, as judged by the organizers. (This allows, e.g., for submitting different planning approaches as separate planning systems even if they are part of a common software.)

For each planning system submitted, a maximum of three different configurations may be submitted.

A modification of somebody else’s HTN planning system is a valid submission if and only if the original author(s) have been made aware of the submission and are consenting.


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