Fast Downward 24.06 released

[Malte Helmert]

Dear Fast Downward group,

we are happy to announce the release of Fast Downward 24.06.

Highlights:

- We have improved the translator in several dimensions. Key
improvements include better error reporting for invalid PDDL, a revised
and faster version of the invariant algorithm and full support for
negated predicates in the goal.

- Negated axioms are now computed in the search component, and only in
configurations that actually use them. This eliminates a worst-case
exponential performance bottleneck in cases where negated axioms are not
used. Heuristics that use negated axioms have a new option
(axioms=approximate_negative) to avoid this computation at the cost of
some heuristic accuracy.

- There are many improvements to the landmark_sum and
landmark_cost_partitioning heuristics. This includes a new theory of
landmark progression that fixes a gap in the completeness in search
configurations like LAMA and can deal directly with cyclic landmark
orders, support for reasonable orders in admissible landmark heuristics,
a cleaner definition of preferred operators, deterministic synthesis of
reasonable orders, and performance improvements. Please note that the
command-line options for landmark heuristics have changed.

- We added a new set of operator-counting constraints
(delete_relaxation_rr_constraints), which implements the
delete-relaxation operator-counting constraints by Rankooh and Rintanen.
The old delete_relaxation_constraints plugin using the constraints by
Imai and Fukunaga has been renamed to delete_relaxation_if_constraints.

- We added the alias seq-sat-fdss-2023 for the satisficing Fast Downward
Stone Soup 2023 portfolio from IPC 2023.

- For developers: planner component objects (such as heuristics or
search algorithms) are now constructed with individual parameters rather
than having all parameters encapsulated in an Options object. (We
mention this primarily for developers maintaining their own forks, as
this change affects more than 200 source files.)


To download the release and to see the full set of changes, see:

https://www.fast-downward.org/Releases/24.06

As always, please let us know if you encounter any problems with the
release artifacts (tarball, Apptainer image, Docker image, Vagrantfile).

Happy planning,
the Fast Downward team