Loki

Loki is a C++20 library for syntactic and semantic parsing of PDDL files.

Supported PDDL Requirements

• [x] :strips
• [x] :typing
• [x] :negative-preconditions
• [x] :disjunctive-preconditions
• [x] :equality
• [x] :existential-preconditions
• [x] :universal-preconditions
• [x] :quantified-preconditions
• [x] :conditional-effects
• [ ] :fluents
• [x] :numeric-fluents
• [ ] :object-fluents
• [x] :adl
• [ ] :durative-actions
• [x] :derived-predicates
• [ ] :timed-initial-literals
• [ ] :preferences
• [ ] :constraints
• [x] :action-costs

Dependencies

Loki depends on a fraction of Boost's header-only libraries (Fusion, Spirit x3, Container), its performance benchmarking framework depends on GoogleBenchmark, and its testing framework depends on GoogleTest.

We provide a CMake Superbuild project that takes care of downloading, building, and installing all dependencies.

# Configure dependencies
cmake -S dependencies -B dependencies/build -DCMAKE_INSTALL_PREFIX=dependencies/installs
# Build and install dependencies
cmake --build dependencies/build -j16

Build Instructions

# Configure with installation prefixes of all dependencies
cmake -S . -B build -DCMAKE_PREFIX_PATH=${PWD}/dependencies/installs
# Build
cmake --build build -j16
# Install (optional)
cmake --install build --prefix=<path/to/installation-directory>

Integration Instructions

We provide a CMake Superbuild project here that takes care of downloading, building, and installing Loki together and its dependencies. You can simply copy it to your project or integrate it in your own Superbuild and run it similarly to the Superbuild project from above. An example planning library based on Loki is available here.

Running the Examples

The examples illustrate best practices on how to use Loki.

The first example shows the incorrect handling of the ownership semantics. The example is supposed to crash when trying to print the domain for the second time.

./build/examples/undefined_behavior

The second example shows how to parse a domain and problem file which is supposed to be used in a planning system where a non-fragmented indexing of atoms and literals is preferred.

./build/examples/single_problem

The third example shows how to detect structurally equivalent problems over a common domain.

./build/examples/multiple_problems

The fourth example shows how to find the matched positions of each PDDL object in the input stream and how to report customized clang-style error reports.

./build/examples/position_cache

Running the Executables

Parsing a domain file and printing it.

./build/exe/domain benchmarks/gripper/domain.pddl

Parsing a domain and a problem file and printing both.

./build/exe/problem benchmarks/gripper/domain.pddl benchmarks/gripper/p-2-0.pddl

Running the Tests

The testing framework depends on GoogleTest and requires the additional compile flag -DBUILD_TESTS=ON to be set in the cmake configure step.

Performance Benchmarks

The benchmark framework depends on GoogleBenchmark and requires the additional compile flag -DBUILD_BENCHMARKS=ON to be set in the cmake configure step. The results from the GitHub action can be viewed here.

IDE Support

We developed Loki in Visual Studio Code. We recommend the C/C++ and CMake Tools extensions by Microsoft. To get maximum IDE support, you should set the following Cmake: Configure Args in the CMake Tools extension settings under Workspace:

• -DCMAKE_PREFIX_PATH=${workspaceFolder}/dependencies/installs
• -DBUILD_TESTS=ON
• -DBUILD_BENCHMARKS=ON

After running CMake: Configure in Visual Studio Code (ctrl + shift + p), you should see all include paths being correctly resolved.

Acknowledgements

This work was partially supported by the Wallenberg AI, Autonomous Systems and Software Program (WASP) funded by the Knut and Alice Wallenberg Foundation.